Essentially, the seeming defeat of Communism was also the seeming defeat of Enlightenment itself.
I think one issue with Sci-Fi is a fatigue with the whole World of Tomorrow™ concept. Considering we've had decades of reality dispel much of the speculation we had in the 20th century, that makes audiences much less willing to suspend disbelief for a Sci-Fi future. Fantasy just *is* and as long as the fantasy world is internally consistent, then audiences seem more willing to suspend disbelief.
I do think Sci-Fi is, essentially, harder to create because it's so closely tied to the limits and restraints of our knowledge. The more we advance, the more aware we are of our limitations. As such, FTL-based stories, galaxy-spanning story worlds, alien-contact tales, and idyllic/utopian futures are harder to accept as plausible. I think this is why, in part, why dystopian stories have taken hold. There's currently no limit to how far a society can fall given future technologies.