Science fiction usually doesn't conform to how the world actually works in the same way pornography usually doesn't conform to the way sexual relationships work. They are both there to tell titillating stories, not describe reality.
It depends on the author I guess. Stanislaw Lem for instance mostly separated his "silly-fiction universes" (e.g. the Ijon Tichy and 'robot fairytales' novels) from his "hard sci-fi" universes (for instance the Pilot Pirx novels) - and there it was mostly about the restrictions of space travel (where space travel is usually just plain old cargo hauling), Pirx never left the solar system because it simply wasn't possible during his lifetime (part of him eventually did - maybe - in his last book 'Fiasco'), instead the Pirx novels were mostly occupied with typical 'space trucker' problems like oil leaks on his rocket boosters, wrestling with space harbour bureaucracy or the occasional humanoid robot going into a mode that could be described as 'mad' or 'depressed'.
Sometimes you might get a SF author who's an expert in a particular field or has a specific hyperfixation, and that one aspect of their stories might be grounded somewhat in plausibility, but everything else turns out to be complete nonsense.
Interestingly there’s also “high” fantasy to differentiate between earth like and non earth like subject worlds, and then even “historical fiction” to describe books that try to be faithful to some degree to some historical time period on earth.
Anyway, this is all to say maybe “how far science-fiction has fallen” might be a narrow interpretation of what’s been happening to fiction in general over the past 75 years. More options than ever, maybe…