It doesn't look like "Asian”( or all Asian cartoons) is because it does not based on "Far East Asian"- however It has strong Inuit/Pacific islander culture color, which still Asian as well.
Therefore I do agree the part it doesn't make sense for Chinese to play the role, since it clearly is not what it based on at all.(Except the bending move). For me it makes more sense if they find a Hawaiian actress for the water tribe girl (or Inuit if they can find one)
That is because their home countries are still in feud with each other.
Japan once invaded China and South Korea, and China basically pisses off all nearby countries (except North Korea), Japan/South Korea/Taiwan/ Vietnamese/Thailand/Cambodia......... etc
but besides that, yes, Asian are racist too.
The story is Asian-based. There are darker skin Asian and lighter skin Asian The water tribe is darker skin so brown yeah if the brown means Inuit/pacific islanders. Ang (Air nomad) is obviously a Tibetan. Earth Kingdom is Mandarin/Qing. Fire Nation is Chinese (Some people say it is Japan but the clothes and buildings style look even more Chinese than Earth Kingdom)
There are plenty of Hawaiian actors/actresses. I mean, if Hawaii Five-O can find so many Hawaiian actors/actresses to play, no reason Netflix not able to find any.