People who complain that making characters a different race or gender to displace existing characters have a fair point. White Nick didn't need to die so Black Nick could exist. Both could've existed. Black Nick could still take over SHIELD.
Thor's name thing bothers me. I always maintain it was his name, not a title, but that aside...you can only have one Thor. There's one hammer. So, that's fine.
My issue comes when someone like Kamala Khan is created and people still whine and cry about political correctness, a term they don't actually know the meaning of.
People blame political correctness for forcing them to, at the very least, cloak their inherent bigotry behind more creative language. Most people who complain about it either don't know what it is, or don't know what it is and hate that they can't just say shit without thinking about the other people in society anymore.
So, yes, it's a debate that can be had. You're not awful if you disagree with diversification by case basis or with good reason. If it's the race/gender that bothers you, then you're a bigot. If it's the shortcut of bad writing, you're making a fair point. However, who can say which is someone's true motive?
Kingpin could easily be black. So could Johnny Storm. They're just guys from America. Black Panther is a black, African male. Making him white wouldn't work. Just like making a film about someone who is inherently white wouldn't work as a black man. If their race/gender is part of who they are, don't change it.
It's really not a complex issue. It's pretty cut and dry. Things like this are confused and made into more complicated issues than they are because people think they have to lend credibility to the stupid. Rather than just weeding out the large swathe of bigoted arguments to get to the arguments against race/gender change that have a point.