Yeah. Of all of the genres of fiction, it's the one that's treated as if it's a completely separate entity with little overlap, even when mainstream critically acclaimed authors move in and out of it.
Definitely, if we're including Fantasy in that genre. Crime and thrillers as well.
I actually saw an article the other day in the Grauniad when I was googling for fantasy novels to try, with a headline like "Should Fantasy and science fiction do more than just entertain?" as if no one in that genre had ever bothered to try it before...