"The Cyberiad" by Lem is full of "medieval dragon witch ghost magic spirit quest" stories, but most of the characters in it are robots, and they travel through space.
"Inversions" by Banks is "just" a medieval quest story with magic unless you know The Culture stories, in which case is a interstellar politics story with high tech.
So even those categorisations aren't that straightforward (I would put both in the SF category, but Inversions is tricky - someone unfamiliar with Banks could read it as a straight-up fantasy novel, and if you don't like fantasy it might feel tedious)
I'm good with a few weird edge cases. Just let me find the majority of sci fi books without having to trudge through vast numbers of definitively fantasy books!
The thing is, it's not a "few weird edge cases". But this seems like an odd "problem" to me anyway - I must admit I've never been in the situation of having to trudge through vast numbers of definitively fantasy books to find SF books anywhere...
The majority are really not that hard to categorise.
In the UK at least, fantasy and sci fi occupy the same shelving. Takes me ages pulling books out of the shelf, and immediately rejecting because they are fantasy.
The majority of the books are fantasy, not sci fi. Fantasy seems to have a much bigger audience in the UK anyway.
I'm in the UK. We must frequent different places, because I've never had that problem.
Well, it's a reasonably big place. It would be surprising if we did frequent the same places!