It's a combination of being it's own thing while honoring the animated series. This isn't a play-by-play carbon copy, which has its pros and cons. It sets up the story well with the background info of what's going on. It does combine aspects of multiple episodes into one, so there are a lot of changes in the series and some things lost. The overall story is kept though. The main events and themes, and important information that make it Avatar: The Last Airbender are still there.
The acting and chemistry could be improved, but the cast choices are good for the roles. They're only room to improve on the later seasons.
I never saw the movie, but I'd venture to say the new live action series is way better (but that bar was low). At least the names are pronounced correctly hahaha