Right.

So we'll start with the observation that I'm hardly alone in this opinion. David Brin wrote what is probably the most famous takedown of Star Wars and later expanded it into a 400-page anthology of critical essays. I'm not going to give you 400 pages (I'm not sure why anyone would), but Jayson Bailey over at Flavorwire provides a good overview:

But that’s the trouble with mainstream science fiction filmmaking these days: there’s no expectation that an audience is capable of putting things together or waiting for a payoff, and there certainly aren’t many filmmakers or executives willing to take the risk. The problem, it seems, is the desire of those who greenlight movies to lump science fiction in with action, and it’s easy to guess why: Star Wars. Before 1977, there were occasional crossovers, but for the most part, science fiction was a genre purely unto itself, concerned with alien invasions and post-apocalyptic scenarios and subtextual parallels. After Lucas mashed up spaceships and swashbucklers, sci-fi was never the same.

Because here's the thing: Science fiction is the genre of "what if." Fables, going back to Aesop, are "what if" stories. The Sci Fi Channel, back before it sucked, even used "what if?" as its tagline. What if a friendly alien came to Earth and was attacked by the Army? What if someone invented a serum that made morons geniuses... but only for a month? What if eugenics and mass media were used to dominate society? The useful thing about "what if" scenarios is you can use them as a funhouse mirror to reflect your culture back at itself, highlighting certain things and diminishing others. Science Fiction is useful as social inquiry. Science fiction is useful in exploring ideas. Science fiction is exploring new worlds and seeking out new civilizations, boldly going where no man has gone before.

Jules Verne was out there for the time. HG Wells? Morlocks and Eloi were all about class discussion. The invisible Man is a riff on Faust. Even Jack London's Big Red One is an exploration of class. And this is what sci fi was doing... up until 1977.

Ever seen Logan's Run? You should; it's pretty much the quintessential sci fi up to Star Wars. How 'bout The Man Who Fell to Earth? One is disco as fuck but poses the question "What if everyone were killed when they turned 30?" The other is brooding and dark and poses the question "what if an idealistic alien were exposed to our consumer society?" Logan's Run came out 11 months before Star Wars; Man who Fell to Earth was 14. But after Star Wars...

Whelp, Close Encounters came out about five months after. It basically established the Spielbergian paradigm of "fuzzy special effects that love us." But there's no "what if?" to it. Alien and Black Hole managed to get out; they were shooting while Star Wars was in wide release. But after that, sci fi was "B movies" and "gigantic blockbusters by George Lucas." A lot of those b movies were ripoffs of gigantic blockbusters by George Lucas. There was no point in making something unless it was a cheap-ass movie or a summer blockbuster and there are only so many summer blockbusters.

I've been in these meetings, with these producers, having these discussions, and ten years ago, the rule of thumb was that sci fi needed to be $2m or less or $100m or more. You'll notice that those two budgets basically eliminate anything of quality. Hollywood learned that you could take a samurai film and put lasers in it and sell it for a billion dollars, so that's all they did from that point forth.

It might be worth it to you, at some point, to check out Harlan Ellison's I, Robot screenplay. It was a big budget adaptation of the book, by Asimov and Ellison, that died an ignoble death as soon as it became clear that science fiction was gonna be 100% a long time ago in a galaxy far, far away. And all those "what if" questions were now going to be "who cares."

We got our I, Robot eventually. But it was a spec script by Jeff Vintar called "Hardwired" that had the three laws of robotics welded onto it. Our tastes for "science fiction", you see, have been so shaped by Star Wars that nobody figured the actual I, Robot could make any money. After all, they made Patch Adams into a robot and it lost a shit-ton of money.