You're acting as though the writers started with a premise that everything in the Eddur is canon, and then were too lazy to get it right. But their premise is that these guys from another part of the universe visited Earth 1000 years ago, flashed a little thunder and lightning, and were worshipped as gods. That means you can have any amount of stuff from mythology be "the bit that the ignorant humans got right", and the rest can be crazy stuff they just made up round the campfire. Thor and Sif, for example: maybe they've been to Earth before, and people just assumed they were a couple. Or maybe they were dating at the time but are now friendly exes. Maybe she changed her hair.

The point is that this isn't a Neil Gaiman or Terry Pratchett story, where the gods are the products of human minds and therefore our myths are correct by definition. These are aliens who've been doing their thing for millennia – if a bunch of primitives got their facts wrong, it's not their fault.

This also means there's no reason (given that they are so inexplicably humanoid in the first place) why there shouldn't be black or Asian Æsir. They don't have to take their physical characteristics after a bunch of dumb humans who told stories about them.