The Buddha, while alive, was very strict indeed regarding the misrepresentation of his Teaching:
"Is it true, Ari.t.tha, that you have conceived this pernicious view: 'There are things called "obstructions" by the Blessed One. As I understand his teaching those things are not necessarily obstructive for him who pursues them'?" — "Yes, indeed, Lord, I understand the teaching of the Blessed One in this way that those things called 'obstructions' by the Blessed One, are not necessarily obstructive for him who pursues them."
6. "Of whom do you know, foolish man, that I have taught to him the teaching in that manner? Did I not, foolish man, speak in many ways of those obstructive things that they are obstructions indeed, and that they necessarily obstruct him who pursues them? Sense desires, so I have said, bring little enjoyment, and much suffering and disappointment. The perils in them are greater. Sense desires are like bare bones, have I said; they are like a lump of flesh... they are like a snake's head, have I said. They bring much suffering and disappointment. The perils in them are greater. But you, O foolish man, have misrepresented us by what you personally have wrongly grasped. You have undermined your own (future) and have created much demerit. This, foolish man, will bring you much harm and suffering for a long time."
So, misrepresentation of the Buddha was happening while he was physically present....and 2500 years have passed since then! And the Teaching, well before KF or DI had ever set eyes on the Dhamma, had already branched into the many varied sects even within the Theravada, Mahayana, Vajrayana (etc) schools.
The suttas in the Pali Tipitaka are the closest and most reliable source of the authentic teachings of the historical Buddha (but would we want any from any 'other' Buddha?). They are probably not perfect, they might have a few corruptions (I am not qualified to judge though), but they are still the best we have. Delusion being so tricky to overcome, we surely need the aid of a Buddha, not just contemporaries who feel they have either rediscovered, redefined, or even surpassed the Teaching of One whom, by all accounts, was singularly impressive in a really huge way. He sent waves through the spiritual dimension of humanity, and the ripples can be perceived even now. I feel them whenever I read the words of the Dhammapada, for example. Such beauty, truth, and power. And the words of the Buddha (as we have them) keep my mind from straying into it's own self-serving version of truth (delusion is very tricky...).
So what I find so irritating about the redefining of the Dhamma that is going on in some circles is the presumption that ANY of us have the same singularly massive spiritual footprint of a Tathagatha. We don't. When a true One arises, we will know (not in this lifetime). Until then, I will continue to use the teachings of the most recent One as my guide.