Nickelodeon had a show that people of all ages and all walks of life watched as if it was "Real Housewives of Everywhere USA". Anticipation for a live action flick was high as the source material pretty much wrote itself.

Then M Night happened.

First, no people of color unless they're villans. Anyone integral to the story that should have been of color (pretty much the entire cast) wasn't.
Second, action sequences devoid of "action" and special effects that looked like they were done in 1984.
Third, this is what "bending" is in this movie: https://www.youtube.com/watch?v=_RpgbZcHk_A

We had the technology to make this movie as spectacular as Avatar from an effects point of view. Instead we got "Flash Gordon"-tier effect.

The movie was so terrible it's probably the reason the animated sequel took so long to come out. Nick likely had to let the crushing disappointment that was MNS-Avatar fade before coming back to salvage the once wildly popular show.
---------------------------

"Where was the peace when we were getting shot? Where's the peace when we were getting laid out?
Where is the peace when we are in the back of ambulances? Where is the peace then?
They don't want to call for peace then.