Matthew Harris 400's page

The sweet spot for me is how things are in the existing core line up to (I think) Horror Adventures. I'd much rather just have the mechanics with a 2 sentence generic fluff explanation, and figure out the rest myself in my own campaign setting. Gnomes "coming from the land of the Fey" is fine. Almost every setting is gonna have some Fey land because it's built into the rules. Fey is a creature type.
"Half-Orcs can be found near Belzken" is too far. Only Golarion has Belzken, and it's a pain to have to tell my players "here's the rulebook we use, but ignore all of this fluff". It's also a pain to pay for pages of a book that I'll never use, (here's looking at you Dead Suns #3. One day I'll pay $15 just to get Necrografts. Today is not that day.)

One of my favorite things about Pathfinder is that the core stuff...

This sounds a bit like a mountain out of a molehill. It shouldn't be that hard to tell your players "ignore all the fluff, this is a homebrew campaign".