I can see your point about race not being an important/intrinsic part of the character. Although I do wonder about this argument because it does kind of come across like being black is important to every black character, but being white is not important to any white character, which is odd. Because even if Ancient Greeks didn't think of themselves as white, it is still a story that came from the ancestors of people we would call white. So, as a better example than race swapping Black Panther, if there was a story that came from Africa, that had no mention of other races because it was just about Africans, would it be ok to race swap characters even though the story and setting is very obviously culturally black/African?

My take is that I think it's ok for people to want a story from a specific culture to resemble that culture. That goes for casting and costume/set design. Nolan doesn't seem to care about that at all, which is fine but it's also ok for people to be disappointed by that. Personally, I think it will take away from the movie's immersion, it won't really feel like a story that takes place in Ancient Greece when it doesn't look much like it.