Edit: Highlights include Leviathan Wakes/The Expanse, The Three-Body Problem, Children of Time, Pushing Ice (and other titles by Alastair Reynolds), Interstellar (debatable, but it's good), Project Hail Mary, For All Mankind, and many more.
I've heard "The Expanse" and "For All Mankind" are supposed to be good TV shows, but I haven't seen them yet.
If you've already read most of the well-known ones, I could give you some recommendations from less well-known authors and self-published authors you probably haven't heard of yet. Though it would help to have some general direction of what you're looking for (military/space opera/other, ftl/aliens?, etc). Allowing for limited FTL handwavyness opens up a lot of space opera titles that elect to otherwise play by hard sci-fi rules.
* Some may recommend "Pushing Ice" over this one for being more "hard" sci-fi, but personally House of Suns was a much more satisfying read.
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…