I understand what you're saying - but how do you build on the colonialism angle in a interesting way while remaining true to reality? I guess they could abandon reality, but they kind of already did that with Jake Sully (going native ain't that common) and that angle's tired
I think the thing I missed most in this movie was... well, to make a Jurassic Park comparison, it would be the Ian Malcolm (Jeff Goldblum) character. Malcolm's character was the only legitimately interesting human element of that story, but he did a lot to add to the feel of the story just because he saw all the horror coming from a mile away, and when vindicated he was just annoyed that nobody else saw it coming.
I agree that the characters were probably too ordinary, and the most interesting ones were the Na'vi, who came across like African tribal archetypes in some places (first time I saw Tsu'Tey, heir to the cheiftain, I couldn't stop thinking that he looked like some nightmare image of a Zulu warrior from antiquity)
Still fun though