You may have read John Harrison's rant on how world-building is useless and counterproductive.
My initial reaction to this is, "Er . . . isn't world-building kind of the defining point of science fiction?" The point of a science fiction story--the reason you'd write a given story in a science fiction setting, rather than a contemporary or historical one--is that the world allows you to do something that would be impossible in a normal, real world milieu.
Maybe he's using a different definition of "world-building" than I am. He implies that "world-building" somehow involves exhaustively categorizing every feature of a world. I don't know of any writer, ever, who's done that. Even Tolkien didn't do that. As an example -- he never actually "finished" his languages.
But he created enough to give his world an underlying structure. Enough so that he could name things "Morgoth" and "Mordor," or "Minas Tirith" and "Minas Morgul," and have a reason for it. The reader need never even find out what the pattern means, but the fact that it's there lends the world verisimilitude.
The feeling of being real. Which is why we read science fiction.