The effects look ok, but theres something wrong with the firebender and the makeup on King Bumi looks like shit.
As a work in progress, it's encouraging to see something that respects the source aesthetic. If this is the final product, it won't be very impressive.
That said, it's all going to come down to writing and acting. We can forgive a lot of unimpressive CG if the show is good.
The only reason this is a topic of discussion is that the live action movie made bending boring and overly complicated. It wasn't the worst part of the movie, but it was emblematic of the source of all the problems: The Filmmakers thought their ideas were better than the source material. Everything from changing races, to changing story elements, to changing the way bending works, to changing how the main character's name is pronounced, all of it comes back to people making decisions to disregard the existing content.
So if they make something that captures the essence of the cartoon, and respects the fans while showing them something new, minor flaws will be easy to overlook. Consider the One Piece show. It took a lot of liberties with the storyline, and many of the practical effects looked silly (looking at you, fishmen) but fans and new viewers loved it because it captured the essence of the original show (and manga).