I feel like I want to go with the Nostalgia Critic on the Airbender movie (my sister made me watch that Nostalgia critic episode; she loves him): It was just too focused on minutiae and exposition instead of all the things that made the original series great, like humor, and character relationships (and awesome bending fights). It was precisely the sort of thing a fan might put out: dedicated to the material, but not in a way that shows that the fan actually gets
why they like it so much. There's exposition trying explain everything, but without convincing the audience that they care about anything that happens in the first place.
And that is the problem. Whether you're aware of the show or you're not aware of the show, the movie is all explanation with no humanity. Why do you think they waited twenty minutes of the film to ask him his name? Because that's not what was most important to Shyamalan. The identity? Who gives a shit? It can't be nearly as important as explaining... and explaining... and explaining... and explaining...
In addition to the incredibly weird decision to just not make the fight scenes as cool as possible. I mean wtf? That's such an obvious gimme it's mind-boggling. When you can't do a better fight scene than a
children's show, there's a problem.
But even watching those fight scenes again, I'm struck by how in addition to being cool, they are also pretty funny (except Azula vs. Zuko, but that's the series finale so that's obvious). It really was a funny show.
Be more awesome if the sound was muted. I can never get used to American style cartoon voice acting (with only a few exceptions). It really feels to me like they have a "for kids" talking down to the audience thing in their heads.
I was like 10 when I started watching this (note: I actually have no clue how old I was when I started watching this), so ¯\_(ツ)_/¯