I don't know if M. Night is done, but it's clear that he doesn't have the personal tool box to both write and direct. The telling of it felt like that of a TV movie.
He needed a filter on this one... someone with experience in adaptation, and it really needed to be condensed and interpreted for the big screen, a la Jackson's LOTR series. A little move here and there would have gone a long way.
Remove Zhao and the Blue Spirit entirely, and introduce Azula as the villain at the outset... that would have been a smarter move. If this was a guaranteed trilogy, he could have saved the reveal of the fire lord and the whole phenomenon of earth bending for later installments.
He needs to be taken off the project, like Hardwick and the Twilight series.