1960 sci fi novel Dorsai imagines a future world where humans have interstellar transportation, but messages can only be sent once a day and combat communication is via whistles and hand signals. I also have been reading Battlefield Earth, the poorly written sci fi novel that started Scientology. It also imagines a future with interstellar travel and nearly free energy, but communication is via handwritten letters and other very slow methods.
I think what sci fi authors consistently misunderstand is that communications and even intelligence like AI is far easier than anything that requires big jumps in energy production like flying cars or space travel. We only have a bit more energy production today than 3/4 of a century ago, but our computers are a thousand orders of magnitude smarter.
I wonder what that portends for the future?