It is common in isekais anime for the protagonist to die and be reincarnated in ANOTHER different WORLD where everyone is white and Asian. Generally the protagonist is a Japanese person who was reincarnated in a fantasy world based on European mythologies in which he starts to live with elves, fairies, elves, etc.
So my question is: how likely is it that someone would complain about a story that takes place in another world where all the characters are black? Would a fantasy story based on African mythology be subject to complaints?
Not at al weird. NK Jemisin’s books, while she almost never describes skin color, unless it’s some extreme, like, obsidian or alabaster, seem (to me, a white guy who grew up in Golden Age sci fi) to be populated mostly be people of color. She avoids describing race - as in skin color - but there are hints that white people, as we have them in our world, either don’t exist or are rare.
It works fine.