Sometimes people ask why is it so important to figure out what were true Buddha’s words, what was the Early Dhamma if there have been living so many enlightened Teachers since Buddha’s age? The Teachers explain us the Dhamma and teach us according to their traditions, schools and lineages and thus convey the true meaning of the Buddha words they say. Thus they equal words of teachers and Buddha’s own words. This is how the commentary tradition started. What Buddha himself thought about this?

Staying near Sāvatthī. “Monks, there once was a time when the Dasārahas had a large drum called ‘Summoner.’ Whenever Summoner was split, the Dasārahas inserted another peg in it, until the time came when Summoner’s original wooden body had disappeared and only a conglomeration of pegs remained. [The Commentary notes that the drum originally could be heard for twelve leagues, but in its final condition couldn’t be heard even from behind a curtain.]
“In the same way, in the course of the future there will be monks who won’t listen when discourses that are words of the Tathāgata—deep, deep in their meaning, transcendent, connected with emptiness—are being recited. They won’t lend ear, won’t set their hearts on knowing them, won’t regard these teachings as worth grasping or mastering. But they will listen when discourses that are literary works—the works of poets, elegant in sound, elegant in rhetoric, the work of outsiders, words of disciples—are recited. They will lend ear and set their hearts on knowing them. They will regard these teachings as worth grasping & mastering.
“In this way the disappearance of the discourses that are words of the Tathāgata—deep, deep in their meaning, transcendent, connected with emptiness—will come about.
“Thus you should train yourselves: ‘We will listen when discourses that are words of the Tathāgata—deep, deep in their meaning, transcendent, connected with emptiness—are being recited. We will lend ear, will set our hearts on knowing them, will regard these teachings as worth grasping & mastering.’ That’s how you should train yourselves.”
SN 20.7

So while the commentaries and traditions might help us to understand Buddha’s words better, we should first figure out what were the original Buddha words and compare any teachings we have heard (whatever famous and popular the teacher is) to the most extant layers of early suttas. If they match then the teacher’s doctrines should be accepted if not the Buddha words should be most important to us.

That is why it is extremely important for us to figure out what was the original Buddha’s words, the Early Dhamma.