You know, I honestly can't critique the story of the first Avatar. A lot of people like to say it's just "Fern Gully/Dances with wolves" in space, but I tend to think that's an unfair oversimplification. Similar beats, but I think the story is a fine example of a Hero's Journey with some spectacular visuals, very good worldbuilding and fairly decent characters and arcs, even if the villain could've been just a tad bit more complex.
It really checks all the boxes, I just think it got a lot of hype so people were expecting "more", but quite honestly, just taking into account sfx alone what more can you ask for? I still remember my first time seeing it in 3D, blew my socks off.