Perhaps because it never did?
Avatar is about colonialism. It's about a foreign power invading another culture and abusing their people and resources. It's something AK touches on, but it's not directly related to humans' relationship to animals or even environmentalism because that's not the story's focus. Maybe if the Navi themselves were responsible for the destruction of their homeland there'd be more substance to that, but humans fighting Native Americans humanoid Aliens is not. Even if the land did ironically replace a show with Pocahontas.
Nobody questions why Pirates are in Adventureland or why Space Mountain is in Tomorrowland. I don't have to explain why the safari ride is in Animal Kingdom, or the bug show, or the animal hospital. If you have to explain it, it's not a strong fit.