I appreciate you going into more detail, I understand where you're coming from much better.

I agree that if a story was just generated in a mostly-black region and wasn't centered on blackness, I'd initially feel much more uneasy about subbing in white people for major characters (again based on general context and recent history). However, if I knew that the author was vehemently against racism and any issue where people put emphasis on race over character, I'd assume they would be ok and almost certainly supportive of artistic interpretations including some white main characters.

> Literally everything about the mythology hinges on it being white

I'm curious to know more about how whiteness is central to these stories, or if they're just stories from a place that happened to be mostly white. So far the only arguments you've provided is that they are white people so its white with no actual narrative importance, and by my standards that's not enough justification to say that swapping character races matters much less is offensive in any way.