Yes, I think there is something in this. Perhaps not so much the Lamas themselves - well most of them - but a two way thing. For some reason Westerners when introduced to Tibetan Buddhism tend to think that it is all about cultivating these religious imaginations you talk about. And they pester the Lamas to give them more and more advanced and intricate things to imagine. Which they think of as "higher practices". Many of the Lamas humour them by giving them complicated things to imagine, intricate vast mandalas - but they are careful not to give them practices that would lead them too much into a world of pure fantasy.

They got this tradition from Indian Buddhism and it is surely related to the practices of Hindu yoga deities. But not thought of as deities, rather as aspects of enlightenment. They are more like poems. Like the vivid images you may get in some of Blake's p0ems, for instance, which somehow affect you at a deep level.

They are meant to evoke compassion and love and wisdom in the practitioner, and such like. And if taught properly, you are taught that the idea eventually is to drop all the visualizations, that the true compassion is not Chenrezig (Avalokiteśvara  as an image or statue of a person holding a lotus flower

Avalokiteśvara  holding a lotus flower. Nālandā, Bihar, India, 9th century CE. Khasarpana Lokesvara (wikipedia)

Or like this

Avalokiteśvara painting from a Sanskrit palm-leaf manuscript. India, 12th century. See Astasahasrika Prajnaparamita Avalokitesvara Bodhisattva Nalanda (wikipedia)

That's just a visual poem to evoke compassion. And there may be an accompanying poem to recite and of course the Om Mani Padme Hung mantra

"Along the paths of Zanskar, the traveller is often confronted with Mani walls. These stone structures are a compilation of exquisitely carved stone tablets, each with the inscription "Om Mani Padme Hum" which translates to "Hail to the jewel in the lotus". "Mune wall col

There would be no point at all in visualizing Chenrezig or Avelokitesvara if it didn't evoke compassion. And at the end you need to drop the visualization, as it can get in the way of true compassion if you always have this image kind of between you and the true nature of compassion.

So the problem with Westerners is that often they are very heavy in their visualizations. And they may be able to imagine Chenrezig in great detail following the instructions of their Lama, but haven't done much by way of relating to the compassion side of it, so it's not evoking much by way of compassion. That's almost pointless. It does have some value, they have the idea that by doing this you are making a connection with the practice, even if you aren't actually doing it properly, so maybe some time in the future you will do it properly.

Most of the "initiations" that Tibetan Lamas give in the West are like this, blessing connections. Not really the proper practice.

My teacher (I don't mean guru, as I haven't entered into a guru / student relationship, but the person who taught me and others in the Nyingmapa Tibetan tradition for many years) - he said that with those mass initiations you get sometimes, in many ways the ones who make the best connection are those who wander in off the street, experience an impressive ceremony, and then go away again. Because they have made that same blessing connection, but without all the hangups of those who tend to go overboard and think they are now something special because they received this blessing and think they are now genuinely doing the practice.

Of course some rare individuals may make an immediate direct connection so they are actually practicing it as it should be. And for them, it may be that visualizing Chenrezig and reciting the mantra immediately evokes deep boundless compassion, and that it is also easy for them to drop the visualization and be left with just a direct connection to that compassion. Others may make a gentle and light connection with no hangups at all, like reading a poem.

But both of these I think are probably rare amongst Western practitioners.

There's also a tendency within Tibetan Buddhism for practitioners, the Tibetans included, to do many practices. There's a saying that the Indian Buddhists - back when India was a Buddhist country - would do one of these practices thoroughly, and realize them all. While the Tibetans would do many practices and realize none.

And - there is no need at all to receive any blessings or do any of these practices as a Tibetan Buddhist. Your teacher can't tell you that you have to do it. That's up to you.

Again some teachers, especially Westerners, may tell their students that they are their guru. But it's not for a teacher to say that. It's always the student's decision whether they want to take on a teacher as a guru, and then up to the teacher whether to accept them. Indeed even if a teacher does not accept their student, still they may be their guru. Because the word guru here is defined by whether the person teaching you is inspiring you along the path in a particular way. You can't make someone into a guru by just blindly following what they say, as some Westerners seem to think.

But if you meet someone who inspires you to compassion and wisdom in the way they teach and instruct you - then they are a true guru for you.  If they aren't doing that, then they are not, no matter what they or you may think. So this idea of a guru is not limited to the Eastern religions but is something common to all religions and none. Just they don't tend to give it a word in the same way.

And a guru in this sense need not at all be a particularly wise or good or sensible person. May be. But you can be inspired along the path even by trees, birds, inanimate things. And you can be inspired by a human being with many flaws and who makes many mistakes, yet somehow they inspire you along the path of wisdom and compassion, and sometimes you can't really see how it happens but know it does.

What matters is whether they inspire you, not so much whether they are able to follow the path themselves. That's kind of irrelevant in a way. In this sense you can have many gurus.

Often an advanced practitioner in the Tibetan traditions may have a particular "root guru" who they follow, especially for instance those who do long multi-year retreats normally do (but don't have to) but not many Westerners are in that situation I think, though many think they are. And if they are, they hopefully have a teacher that can explain it properly to them. 

The idea of a root guru is that they are someone who is not you, basically. Wh0 you also find inspiring. Deals with the issue that you may feel the path is your own doing, that you are not just relating to compassion and wisdom, but that somehow it is you yourself creating it. If you have that attitude, you can never connect to it properly in its boundless sense. Having someone else you follow as a root guru means it is not all "up to you" which makes it easier to connect to the unbounded compassion and wisdom, instead of to a pale constructed shadow of it that you make up yourself in your imagination.

A guru in this sense, even though they are telling you to do things as this "not you" inspiration - they can never ask you to do anything that goes against compassion or wisdom, or the dharma - the teachings of the Buddha. If they do, the student should ignore them. A good teacher will explain this. The whole thing of a root guru is intended to inspire wisdom and compassion and give you a direct connection to the path the Buddha followed, and that's its only purpose.

And the visualizations of Tibetan Buddhism - when they get to the intricate stages that Westerners often practice them with - instead of just relating directly in a simple inspiring way to the image and the mantra as ordinary folk not advanced practitioners can do or that person who comes off the street, goes through an impressive ceremony and never thinks much about it again. If related to in that light way, no problem. But the truly "advanced" practices are meant for students in some close guru / student relationship. And in that case your teacher would know you very well and is like a doctor prescribing some particular practice because he or she knows that you need it, perhaps some obstacle or difficulty arises in a long retreat for instance and the guru will tell you to do some particular practice to overcome it.

In that sense, the Westerners who do all these practices are a bit like ordinary folk taking insulin because they know it is good for diabetics, even though not diabetic themselves. It's not going to do much good if you don't need insulin, might even harm you. And the Tibetan Lamas are for that reason careful not to hand out the ones that are needed for especially intricate and difficult situations that arise during long retreats, but instead, ones that are more like placebos or coloured sweeties :). And if you are a Western practitioner, it's really silly to ask for more and more advanced intricate practices. It won't do you any good, not if they aren't the right ones for you.

And, again as my teacher taught me, these are all just medicines to address various issues that arise in the ordinary simple meditation that is common to all branches of Buddhism. If you relate well to that practice, the breathing meditation, and no problems arise, well there is no need for any of these visualizations :). The visualizations may help you to connect more quickly and directly to compassion, wisdom and other good qualities. But for some people, well, the ordinary sitting meditation also does that, or does so as much as they can connect at all.

Many of Buddha's disciples connected directly, immediately. In some cases just by hearing of his teachings by hearsay from someone else - according to the sutras. They didn't need these elaborate practices.

So, if you find you connect to meditation in that way - that it is inspiring to just meditate and that this is the only practice you want to do - and you are surrounded by others who seem dead keen on these intricate visualizations, well you can think of the Buddha and his first disciples as a reassurance that it's just fine to continue with the basic "beginner's meditation" as your main or only practice. Or think about the simple practices of Therevadhan and Zen Buddhism. And if you have a good teacher and you say this to him or her, he or she will surely encourage you to continue along this simpler path.

And you can still be inspired by the images and mantras of Tibetan Buddhism, in that light way, as like beautiful poems - if you do find them inspiring. No need to do the practices to connect to them in that way. And if you do approach it in this way, with this light approach, it will help if later on you do end up doing a long multi year retreat or whatever and need to do some of those practices for whatever reason - then you may be able to connect to them in a lighter way, so that they help with whatever issues arise without becoming a big heavy practice with hangups of its own which you then have to address as well.

Also just to add a bit about the idea of yidams in Tibetan Buddhism, from a comment to another answer here:

TIBETAN LAMAS ARE NOT DEITIES

Tibetan Lamas are not deities at all. That would be as absurd in Tibetan as in Zen Buddhism. Obviously they die, they get old, they are humans like everyone else.

When they say the Dalai Lama is an embodiment of Chenrezig, then that means, embodiment of compassion. That's what it means. To Tibetans who are inspired by him in that way, they see him as embodying compassion in a particularly pure form.

Not that he is that particular iconographical figure - which would be as absurd in Tibetan Buddhism as in Zen Buddhism - is obvious he doesn't look like that either :).

And Tibetans will say to each other "You are Chenrezig" if someone does something especially compassionate - recognizing that in doing so they are expressing their compassionate nature which we all share and which is shown iconographically by Chenrezig in Tibetan Buddhism. So the compassion they see in the Dalai Lama they also see in everyone else who shows compassion. Including of course non Buddhists.

And yes some particular Tibetan reincarnate Lamas have got associations with particular aspects of enlightenment - but that doesn't mean the Dalai Lama "is" compassion. And he like all of them will practice meditations associated with the boundless qualities - compassion, wisdom, love, sympathetic joy etc. As well as many others.

In most branches of Tibetan Buddhism as in Zen Buddhism and other mahayana traditions, they see us all as having the potential of a Buddha. That these qualities are ones that we all share, and indeed that we all actually have that boundless compassionate nature and wisdom without obstruction, if only we could just drop the confusions that hide it from us. And the confusions themselves which obscure our true nature from us, they say are insubstantial, nothing there at all, building up structures upon structures, but they also aren't even there really, all just confusions. Yet so hard to let go because we have clung to them so strongly, and that clinging itself is also just as insubstantial if only we could see it. Can't willfully let go though. To try hard to let go will just make it stronger. The letting go has to come somehow from outside of your ordinary sense of yourself which we struggle so much to maintain and support.