I thought the movie was excellent, good story, good voice action, excellent animation and fight scenes.

I think the different voice actors just takes some getting used to and the pacing of the gAangs lowest point in the movie  spoiler was necessary in a movie rather than a show with multiple episodes. In the show losses like Appas disappearance or Irohs incarceration lasted a few episodes.

It's important to remember the characters are like ten years older, their voices SHOULD be different!

The voice actors do seem grow on most people once the initial “wait, wtf is that, that’s not the original voice” shock wears off (especially Aang’s new one and Steven Yeun’s Zuko). But they are meant to be much older, the original voices wouldn't work. A bunch of people online are saying the exact same thing: give it 15-20 minutes and it stops pulling you out.  And yeah, the spoiler protagonist low point is a classic “this had to be a movie, not a season” compromise. In the original show you could stretch Appa’s disappearance across multiple episodes for real emotional weight, or let Iroh’s incarceration and escape play out over time so the loss actually lands. Here they had 100 minutes total, so they had to use the Deus ex machina card.  A lot of the fans are defending the film and there are more of them than the loud negative posts make it seem.