So what you are saying is because you don't mind altering the setting, no one should?
I'm honestly, truly surprised that the idea of setting fidelity is controversial. I guess that is something that happened in the play culture along the way that I missed. Which is weird since I run regularly at cons and have a player pool numbered in the dozens.
Or, possibly, it's not a representative opinion at all and 2 or 3 people in this thread are trying to sell something that no one else actually ascribes to. Hmm...
Some people have made comparisons of their homebrew settings to works of fine art. That comparison, to me at least, hints at the sort of recurring ideas we see in this thread with how some GMs perceive their settings and any player-proposed additions. GMs claim to put in so much work (for something that is probably not all that great), and one or more player may want to add something to their artwork so they can enjoy it more? The outrage! The artwork is without blemish. It would look outrageous with this odd addition to the piece! (As if famous paintings regularly don't have such odd additions thta make the memorable, unique, and beloved.)
In many respects, it reminds me a lot of the Lego Movie, with a fair number of GMs in this thread seemingly arguing in favor of President Business's worldview over against the message of the movie.
IMHO, when I as a GM present a curated list of ancestries to the players, it represents the beginning of the dialogue or negotiations with players about the setting elements. I may have done the lion's share of the work for a homebrew setting, but I also want to make a setting where the players have fun. I think that players are entitled to fun at the table and have their table time respected as well. Ancestries are a part of the setting that impacts them and their character choices. If the players are good with the curated list, then there are no need for further negotiations. If there is one or more player who wants to play something not on the curated list, then we may need to talk. There are multiple ways to resolve this. All of them involve coming to that discussion with an open mind and a willingness to change things.