I feel like people expect a bit too much from Avatar, that because it's insanely popular it has to be insanely deep, groundbreaking, etc.
They're just popcorn movies. Pretty, popularist blockbusters with a straightforward but universal message, geared to entertain a wide audience.
And that's all they need to be. Not everything has to be Citizen Kane, there's room for movies that are just simplistic fun.