A few observations about science fiction worldbuilding, accumulated over years of reading too much of it:
In fantasy, magic is in the world. In sci-fi, the world itself is the magic trick. The setting isn't backdrop. It's the thesis statement.
Ted Chiang's stories are worldbuilding masterclasses in compression. He establishes the rules of a world in the first two paragraphs and never explains them again. You either keep up or you don't. Most writers could cut half their exposition and lose nothing.
There's a habit in sci-fi writing of over-worldbuilding the technology while under-worldbuilding the social systems. You'll get twelve pages on how the FTL drive works and zero sentences on who raises the children or what happens when someone dies. The ship has artificial gravity but no religion. That's not a future. That's a tech demo.
William Gibson figured out something crucial about near-future fiction: don't explain the slang, don't explain the tech, just let readers surface in a world that doesn't know it's strange. The first chapter of Neuromancer drops you into Chiba City with no orientation, no glossary, no hand-holding. The world doesn't care if you understand it. That's what makes it feel real.
Becky Chambers builds worlds where the technology is solved and the problems are interpersonal. The Monk and Robot series, the Wayfarers series. This is harder than it looks because you have to create stakes without crisis. Most writers don't know how to generate tension from kindness. Chambers does.
Fantasy invents from scratch. Sci-fi asks what happens if we keep going. One builds a new house. The other remodels yours while you're still living in it.
Philip K. Dick wrote worlds that felt paranoid before the paranoia was justified. Precrime in Minority Report. The false reality in Do Androids Dream of Electric Sheep? His settings weren't decoration, they were the argument. Every room in a Dick novel is a room that might not exist.
The best sci-fi worlds change one fundamental thing and let the consequences ripple. One change. Ursula K. Le Guin changed one thing about gender in The Left Hand of Darkness and then spent the entire novel watching what happened to pronouns, to politics, to jealousy, to war. One variable. Infinite downstream effects.