Realistic Hard SF has to deal with Accelerating Change making technology vastly powerful yet still limited. The hardest thing to write about is cognitively enhanced humans or any other entities (AI, aliens, etc.) exceeding human cognitive limits. JW Campbell famously said it couldn't be done, but without that depictions of the future or wider universe fall flat. Vernor Vinge became the master of such SF and showed several ways to do it. I recommend everything he wrote! Good Hard SF requires an author who has a good grasp of science without that stifling their imagination. It's easy if you cheat but Science Fantasy is unreadable by the science literate folks who frequent HN. Good Hard SF is out there, with and without spaceships, but you'll have to hunt for it - and thanks for all the recommendations here!