It's fine and very well done, but it's just not my interest. If Avatar was a single, contained attraction in Tomorrowland I'm sure I'd enjoy it enough, but I don't have much interest in walking around and pretending I'm on Pandora. I'd much rather be immersed in American (and global, although to a lesser extent) history, geography, and culture. These are the aspects I love most about Disneyland and DCA. This is also part of why Galaxy's Edge fall flat for me even though I love Star Wars and quite enjoy Rise of the Resistance.
I'm perfectly happy to play make believe and pretend I am a cowboy, astronaut, or buccaneer, but that's because those roles are real even if I am (or rather, a child is) doing make believe. By pretending to be a cowboy, a child learns about how real people lived their lives in the Old West, and still do today in Montana, Wyoming, and even down in Mexico and Argentina. The same rational applies for pretending to be an astronaut or a pirate, as through play the child comes to learn what these other people have done and continue to do. There is an inherent value in understanding other people and their cultures, so even though Frontierland, New Orleans Square, and Tomorrowland are all make believe, they are making believe about something ground in reality which gives them substance.
Avatar, however, is devoid of reality. Every aspect of it is make believe. To then have a make believe of pure fantasy is not to say it is void of value, but it is of a lesser value. Although there is a valuable message about conservation and racism in Avatar's theme, it is far less interesting than Pocahontas or Dances with Wolves because the latter two are rooted in reality. Consider also this: Pretending to be a Jedi fighting a Rancor is fun and can bring a lot of good to a child, but it is less valuable than if he were to be pretending to be knight fighting a dragon. Both are ultimately make believe and have their element of fantasy, but the latter is rooted in truth and history giving it greater weight. To take it further, it would be even better if that child was pretending her was a knight fighting for Charles Martel against the Saracen Army at the Battle of Tours.
Perhaps it's clear I'm deep into educational philosophy at the moment, but this is really just long winded answer of me basically saying shadows of reality are better than shadows of fantasy. Neither shadows are real, but one at least mimics something real which gives it greater weight. For that reason I prefer lands like Main Street USA and Grizzly Peak over Galaxy's Edge or Pandora.