The Witcher isn't in Medieval Poland though, it's in a fantasy land.
Rings of Power was far more dumb because there's black people, but only in a few extremely important roles. Almost as if there's some sort of reverse curse going on, where a baby pops out black, and they immediately make it their king/queen. Or more likely, they realised very late on that they'd made a very white cast, and made a few last minute changes.