Especially the denomination "speculative fiction" which is grossly abused in recent years, I find.

In French, we still use the equivalent term to differentiate stuff like space opera from proper Sci-fi and books like 1984, Brave New World, or alternative history.

It's silly enough to label Fantasy as spec fic, but the way it's broadened to include the likes of mythology (properly religious texts, or "national"/cultural epics), Alice in Wonderland, novels like Foucault's Pendulum (a thriller) and about anything with magical realism incorporated is just hilarious, like people who enjoy the sci-fi/fantasy genres have a complex of inferiority in the face that these modern genres of fiction have not yet produced enough works recognized as masterpieces of literature (and those often written before the coining of the genres, like Brave New World) and most are being snobbed by the most pretentious literati, so they "steal" classics to put on their list, like giving a coat of varnish.

I rather see (like the thinker J.J. Pelletier) sci-fi/fantasy and most what gets called "genres" (incl. thrillers) as modern branching outs of the original novel traditions. Their common direct ancestor is the novel itself, then it's fiction. There's no direct filiation between any genre and the ancient epics (all fiction has more in common in purpose with folktales and theater, aka fiction inspired by myth, than with epics and myth themselves, for that matter), except through the main tree of literature's evolution. IMHO, anyway.