How much of this is due to the collapse of the Modern Ages? Recall that the modern ages were bourgeois, industrial, and scientific, and it is no surprise that a type of fiction developed that featured imaginable technological innovation as a key background element. In early genre fiction, it even comprised the foreground!
But with the post-modern shift of emphasis
- from matter to form,
- from logos to icon,
- from reading to seeing
It was around the 1950s, historian John Lukacs noted in Outgrowing Democracy, that the circulation of Psychology Today exceeded that of Popular Mechanics, something that would have astounded(!) folks from the early 1900s. Thereafter, the psychology of a story became steadily more important than the mechanics or gadgets. That's certainly not all bad. Stories are better written -- but the speculative science or technology has dimmed. Partly that is because newer writers don't know enough about science to write well about it. Hence, more and more fantasy. Fewer writers are physicists or chemists and more are lit-majors and critics. The form of writing has improved even as the matter has not.
This is in line with that other change of the 1950s: the replacement of "I think that...." with "I feel that...."