On further reflection -- well, you get great classics of SF like 1984 and Brave New World. And you consider why those got accepted in academia. And you may notice that, being dystopias, they are about the contemporary world, not about the future. They're not about escape.
And I have run across many critics who interpret all fantasy works as metaphors for more mundane stuff. Indeed, I have run across one that said of a certain work that if it can't be interpreted as something about the modern world, it is thereby excluded from consideration as "serious literature." (The logic is apparently that "me and mine" are serious, and everything else in the universe is frivolous.)
A lot of people, academic as well as otherwise, aren't really interested in the escapist impulse. They don't want to get out. So they pick and chose among fantastic works those that most fit their real taste in literary, and not for their fantastic elements at all. Kinda limits their ability to distinguish between good and bad works, being blind to what they are attempting to do. (Attempt being a key word; many works fail most ignominiously to actually get out.)