The attitude here is that writers should tread lightly with marginalised cultures that they don’t belong to: don’t try it if you’re not fully prepared to research heavily, to accept insider input, and to give credit where it’s due. I agree with all of that (especially since some marginalised cultures have sacred elements that are closed to outsiders, period). But I’d like advice on handling historical non-European civilisations like Pharaonic Egypt, Sumer, the Phoenicians, and the Olmecs. I’d figure that cultural appropriation would be less of a problem for cultures whose members aren’t alive to be harmed. But even assuming that’s the case, I’d want to avoid whitewashing or stereotyping those cultures and to research them using sources that aren’t too Eurocentric. Do you have any thoughts of your own?
The big thing to keep in mind here is that there are many cultures that we may think of as dead, but actually there are living people associated with the culture. For instance, you don’t want to treat the ancient Inca or the ancient Aztec as cultures as having no people, because there are still those in the Americas descended from these empires who have inherited much of those cultures. I’m guessing the same is probably true of Pharaonic Egypt.
In most cases, it’s better to err on the cautious side and look for the living descendants. People from related cultures can also be relevant. A dead Native American tribe, for instance, is not something I would recommend writing about, as that would probably be upsetting to current day Native Americans from all the living tribes.
At this point, we don’t recommend using a full setting from a marginalized culture at all unless you’re part of that culture or you have the resources of a full movie studio or something, just because it’s that hard to get it to a place where the people of the culture are okay with it. I’m sure there are rare exceptions when it would work out, but we don’t want to set people up to fail.
But theoretically, yes, a culture that’s actually fully gone would be less sensitive, but as you said, I would still try to treat it respectfully.
Best of luck,