The main traditions of Buddhism are based on the sutras. Buddha didn’t actually say to ignore sacred text. What he said was more subtle than that. The text that is often used as a basis for the idea you can do anything that feels right and call it Buddhism is the Kalama sutra. It’s rather long, but is summarized here by a translator:

“Although this discourse is often cited as the Buddha's carte blanche for following one's own sense of right and wrong, it actually says something much more rigorous than that. Traditions are not to be followed simply because they are traditions. Reports (such as historical accounts or news) are not to be followed simply because the source seems reliable. One's own preferences are not to be followed simply because they seem logical or resonate with one's feelings. Instead, any view or belief must be tested by the results it yields when put into practice; and — to guard against the possibility of any bias or limitations in one's understanding of those results — they must further be checked against the experience of people who are wise.”

Kalama Sutta: To the Kalamas

So there is nothing wrong with having texts. It’s just that you don’t follow them just because they are texts but test them by the results they yield and also against the experience of people who are wise.

And in fact all the main traditions of Buddhism do have texts and they also have other systems to make sure they are passed on authentically. And the texts, called the sutras, are actually used for just the reason you mention, to make sure we are following Buddha’s teachings correctly. That is to say - that we are actually listening to what he said. Not that we have to do what he says unthinkingly, but to actually listen to his teachings.

It helps guard against those who may say wild and extraordinary things and claim they are “Buddhist”. You can go to the sutras and say “How does what you said fit in with what the Buddhist sutras say”?

So, the complication is that there are different collections of sutras and they don’t all say the same things. The oldest sutras are the ones in the Pali Canon. These may well record the actual teachings of the historical Buddha. There was no writing in Northern India back then. But they had people who were excellent at memorizing. Also - they memorized millions of words, not just as a list of ideas, like a story or narrative. They memorized them word for word. They actually checked that by reciting them in unison together with each other.

It’s generally agreed by everyone that the ancient Vedas were passed on in this way. There are some who say that the Buddhist Pali Canon was not passed on like this but I find it unconvincing myself.

The Buddhist sutras themselves in the Pali Canon say that they also were passed on in this way describing the monks in the Great Assembly after he died reciting the teachings in unison together just as the Brahmins do for the Vedas. Also, when the texts were finally written down, they were pretty much word for word identical in places as far apart as India and China with no evidence that this was due to them copying each other.

Also there is lots of internal evidence that the Pali canon was composed during the historical period appropriate for the Buddha such as the technology described in the sutras, the political geography described (which changed rapidly after Buddha's death), the lack of any mentions of South India which would have been well known not long after Buddha's death and many other very strong arguments in favour of authenticity.

So, well I think myself that is pretty good evidence. Some even of the Pali Canon sutras were composed later (by the same evidence that shows that the others were original). But most date right back to the Buddha. So if you want to follow the teachings much as for the historical Buddha taught them, then look for a Therevadhan teacher, who uses the Pali Canon as their collection of sutras. The monks wear yellow robes.

Other sutras were attributed to the Buddha and his followers, but actually composed at a much later date, these are the Mahayana teachings. So, you might wonder, why would anyone follow those?

Well the thing is that the Buddhist teachings are an evolving thing. Do we follow the teachings as he taught them 500 BC or whenever it was, before invention of writing in northern India? Or do we follow them as they were developed many centuries later in India? Those who follow the mahayana sutras say that these teachings are actually either inherent in what Buddha taught - or maybe even that he did teach like that to some of his students, but those teachings were not recorded in the Pali canon at the time, and centuries later, somehow transmitted all that time from teacher to student, the teachings got written down, backdated to the Buddha. Or perhaps they arose anew at a later date but arose out of his teachings?

Nobody can really say where they came from. But they also lead to a body of texts which are used by the Tibetans, Japanese etc. They are more like an extension of the Pali canon. Vast collections - the Pali Canon itself is huge the size of an encyclopedia. There are many ancient commentaries on them too. Buddhism has been a scholarly tradition since the beginning, really. The first Buddhist university dates back to several centuries before the first universities in Europe. The first university in Europe was University of Bologna founded in 1088.

The first Indian university was the great Nalanda University in northern India. It started as a Vihara founded by King Ashoka several centuries BCE[16]. During the second to third centuries CE the monastery there was gradually transformed into a "Temple of learning" like the medieval monasteries. One of its most famous early students was Nagarjuna, around 100 A.D. The Nalanda University itself was founded by Kumaragupta who lived from AD 415 to 455.

It was a residential university consisting of six colleges already at the time of Xuanzang (602 - 664 CE), increasing to eight colleges by the time of Yijing (monk) (635-713 CE) by which time it had 300 rooms. Its staff included many famous scholars including Dignaga, father of the medieval system of logic, Dharmapala, Santarakshita and Padmasambhava who was professor of Tantras there. It was a seat of learning of international renown at the time with students from places as far away as China, Japan, Tibet, Korea, Java and Sumatra, with 57 students from China, Japan or Korea recorded between 629 and 671. It had between 3,000 and 5,000 students. Though the number of books in the great library of Nalanda was not known, it is estimated to be in the hundreds of thousands.

The Mahayana sutras date back to before then, to the first few centuries CE. Then in the Tibetan tradition at least there’s the idea that new teachings can arise with the inspiration of Buddha - that they are as if Buddha himself taught them, though newly composed. Because they are teachings of awakening and there’s the idea that even if you are not Buddha you can connect to the teachings of awakening, that an inspiration of that nature can break through into your life. But of course you have to be very careful about that because it could easily be a negative inspiration. So to test these new teachings that keep arising, they test them against the Mahayana sutras.

So - that also is authentic, as a way to practice Buddha’s teachings.

They teach in different ways. The Therevadhan path tends to focus on the noble eightfold way, on things you can do to sort out your own problems which is of course where we all have to start. It is all very well having grand plans to help everyone in the world but that’s not much use if you neglect yourself and brush over and ignore all your failings and negative qualities and rush ahead kind of charging into situations based on the idea that because your motivation is good, somehow it is going to work out.

The mahayana path is generally focused more on compassion and wisdom for all beings as your motivation you try to relate to right from the beginning.

It’s not that either is better than the other. Compassion of course is important in all aspects of Buddhism, as is wisdom. It’s just a slightly different focus really.

The Therevadhan teachings also tend to be rather simpler. Which can be good. Both in terms of the understanding of the world where some of the Mahayana traditions can get immensely complex - and the path for the way you relate to others and open out to others, and the imagery too, the Mahayana traditions can become very complex. But maybe for some people they don’t need all that complexity. Maybe some very simple teaching is all they need and the rest arises naturally?

There are simpler teachings within the Mahayana too, for instance Zen Buddhism is famous for the simplicity of the way it is taught. Despite this simplicity it is still a sutra tradition. It is based on essentially the same Buddhist ideas. It is just that the ideas are often taught in a much simpler way. You get teachings like that in any of the traditions, but the Zen Buddhists kind of specialize in those very simple approaches.

So it’s really a matter of what works with you. Any of the main traditions that rely on sutras are authentic. They all claim a lineage back to the Buddha himself, from teacher to student. They all have the same core ideas and similar core sutras.

For those who become monks or nuns, the Therevadhans are the most strict, observe all the rules, even the most minor ones, if they can. The Mahayana ones tend to be less strict, of course keep the most important vows but for instance, may not wear a robe at times, may eat food after midday (one of the rules is to never eat after midday), etc. Buddha said that some of the rules are minor and can be ignored but he never said which, by tradition Ananda forgot to ask him. So Therevadhans tend to err towards caution and treat them all as if they were major if at all possible. While the Mahayana monks will drop the ones that seem minor, including even such things as whether to wear robes, if they feel that they are creating barriers in how they to relate to others in society, making things awkward for others in any way and so on.

The Japanese “monks and nuns” are the least strict. They take a vow based on the bodhisattva vow which means they don’t have to be celibate - they don’t take a vow of celibacy and indeed are often married. But they call themselves monks and nuns because their lives are dedicated to the path of the Buddha.