Most of science fiction is pure fantasy.
Seriously. Take my own story A Darkling Sea. It involves humans traveling to another star system and interacting with aliens. That's fantasy, right there. There's no way to actually travel faster than the speed of light, and we have no evidence of any other intelligent life in the Milky Way. I might as well have written about people sailing a magic crystal galleon to Elfland.
Sticking to "hard science" is no help. By the time humans can travel to other star systems, they won't be human, not in any way we would recognize. They probably won't even have permanent physical forms, for instance. It's much simpler to travel between stars as data. And a future human civilization which is willing and able to spare the energy to launch starships — even if it's a once-a-decade or once-a-century shoestring operation — must still have access to energy and resources on a scale we can barely imagine. A "realistic" story about interstellar travel would be a tale of gods, not men.
So we're not going to fly off to Earthlike worlds beneath other suns and start homesteading. We've discovered plenty of extrasolar planets, but only a handful have even the potential to be habitable by something we would recognize as alive. Nor will we terraform planets into new Earths. The effort and time scales involved are simply staggering, and the justification for all that work simply doesn't exist. In another few decades the big problem for humans will be depopulation.
Don't even start about time travel.
Well, what if we retreat to a more sociological view of science fiction? Fiction about the impact of new technologies on society? But that's pure fantasy, too. To understand the impact of a new technology on a future society the author has to have a complete understanding of that future society and then of how the technology would affect it. Nobody really understands present-day society, let alone a hypothetical future.
We're not really exploring taboo ideas and "dangerous visions," either. For the most part, science fiction writers are desperately conventional. Example: suppose it were possible to accurately determine a person's aptitudes and know in advance what job he or she is best suited for. That's extremely likely to occur as we learn more about the brain. Suppose someone were to write a story set in a future where being assigned to a career was the norm. What story would they write?
I can predict with 99 percent certainty that the story would be about someone defying the system, and overcoming adversity to do something the brain scans say they shouldn't be good at. In short, a story repeating the shibboleths that have defined Western liberal society for the past two centuries. A story so brave and transgressive that Washington Irving and Sir Walter Scott would nod approvingly at it.
You want edgy? You want "transgressive"? Let's see a story that doesn't reinforce the Western college-educated progressive conventional wisdom of the Current Year. Let's see a story defending intolerance, or fundamentalist religion, or inequality. The only really transgressive writer I can think of is John Norman, and guess what? He is reviled, because his fiction actually does violate contemporary norms. It's icky. We don't really like that when it happens.
So what are we science fiction writers doing, if we're not depicting the future or exploring new ideas? Well, we're telling tales of pure fantasy, but we live in a "scientific" era so we dress up our fairy tales in spacesuits.
And that's okay. Storytellers have to fit their stories to the audience's understanding. When Homer wrote of strange creatures and exotic islands, he had to send Odysseus off to the remote and mysterious western half of the Mediterranean (and even then he put the whole voyage into a tale-within-a-tale narrated by a character famous for his skill at lying). When an anonymous English monk translated Beowulf into Old English, he also changed it to suit a Christian audience.
G.K. Chesterton once said, "Fairy tales do not tell children that dragons exist. Children already know that dragons exist. Fairy tales tell children that dragons can be killed." Science fiction carries on that tradition. We tell our readers that the dragons of an uncaring cosmos can be overcome. The monstrous distances, the demon of entropy, the terror of discovering that we are nothing but animate matter. We show those dragons being beaten. It's worth doing.