So there literally is no basis for what amounts to the following creative vision you are arguing for beyond... not what most people would like...
No, there is, you just stubbornly refuse to consider it.
There is a gap--a
massive, MASSIVE gap--between:
"We do X thing because X thing gets the largest number of paying customers"
and
"We did X thing because it actually matches our explicitly-stated goals."
Avatar: the Last Airbender being about Asian ethnic groups is not what would get the largest number of paying customers in the United States. That would be having
white characters. As has been the case for ages and ages, because white people are still narrowly the majority.
But the people who made Avatar didn't do that. They had a clear, specific vision, and they followed it. They were true to the art (to an almost ridiculous degree--all depicted writing in A:TLA is actual Chinese that says more or less what it should, and writing from ancient times
is actual ancient Chinese, and say to the best of our knowledge more or less what it should.) They didn't pander. They didn't make something
safe and
inoffensive. They had a character suffer a psychotic break "on camera." They had legit actual horrible things in a kids' show.
And it was
awesome.
That is a demonstration of what can be "good for the art," without being what is
necessarily best for the company that made it. Making Avatar was a big risk--and it ended up paying off. Making Korra...well. It's a lot more controversial.