This isn't just about the player and the GM. Lots of players, myself included, do get annoyed when other players insist on a character concept that doesn't fit the genre or the GMs setting. Obviously there needs to be buy in with the group for the campaign to function. The more threads like this I read, the more I think that is a fundamental dividing line in the hobby more than anything else. Neither side is bad for wanting what they want. But some people do like the characters to be expected to fit the campaign concept, the world or the genre, others prefer for players to have greater say in what is a good fit.
One issue that always seems to get ignored in the conversation is that when I think of "curated" campaigns (homebrew, DIY), I am not really concentrating on exlcusion.
Yes, exclusion of some standard things does accentuate what remains. But in my experience, most DMs that go to the effort of having a curated campaign are also altering and adding things to their campaign world as well!
I feel like, far too often, people conjure up this image of some tyrant, standing athwart the PHB and the DMG, yelling, "Stop, there shall be no dragonborn here, for I do not allow them to pass through these gates to my pristine world!"
Really, though, the DMs who have spoken up have discussed (at length) the custom races and/or classes and systems that they have added to their campaign worlds. The homebrew and 3PP material that would not normally be available.
I think that this aspect gets (sadly) overlooked.