Their message did not seem to reflect that sentiment

DiMartino called exiting the project “the hardest professional decision I’ve ever had to make,” adding: “Netflix’s live-action adaptation of ‘Avatar’ has the potential to be good. It might turn out to be a show many of you end up enjoying. But what I can be certain about is that whatever version ends up on-screen, it will not be what Bryan and I had envisioned or intended to make.”

But apparently it was mainly due to creative control. Netflix wanted to go darker/grittier with possible white actors, explore romances, etc while the original creators wanted it to stay true to the childrens story