Pedantic
Legend
I think this is just the discoverability problem clashing with widening readership and genre splitting. For a specific kind of reader, the was certainly a time you could really pick up a random book in the fantasy section at a library or bookstore and more or less know what you were getting within a certain band of expectation.Is it? What do you base this on? Do you mean re: other stuff getting called "romantasy"?
That's changed from both the supply and demand sides. More (and more diverse) people are writing books and more people are reading them, which is a good thing, but changes the experience if you were in a more narrowly targeted group to begin with. What "fantasy" or "sci-fi" entail as genres has expanded, less in the core content and more in what story structures or tropes are no longer normative. We're seeing more kinds of stories with broader focuses using fantasy trappings, especially as self publishing pushes more and more content out to begin with.
This is an insane thing to recommend at 4 hours, but I found Laura Crone's excellent essay on Lev Grossman's The Magicians incredibly clarifying on this point. She loved those books and I found the one I read very disappointing; she explained exactly why that mismatch occurred, left me feeling absolved of missing anything, and I thoroughly enjoyed the secondhand experience of her enjoyment which I was never going to get myself.

