No world-building except that necessary for the story.
Fantasy does not need complicated genealogies, fully-worked-out artificial languages, or laboriously detailed history. Freed of such distractions, fantasy flies. Fantasy is
Q: “So you’re on a crusade against world-building?”
A: Not necessarily. There’s no need to choose one approach; that would be like saying that a toolbox should have either a hammer or a screwdriver, not both. However, one might suspect the detailed world-building era was just that, an era, a historical episode in fantasy and the other world-building genre, science fiction.
Think of the best-loved world-building works in fantasy and sci-fi. In fantasy it’s The Lord of the Rings and in sci-fi it’s Dune. The reason people admired the world-building in The Lord of the Rings was that it was the first work in fantasy to feature such detail, and Dune was, if not the first, one of the first in sci-fi to feature it. That is, a lot of the appeal was the novelty. More than half a century after The Lord of the Rings, and more than a third of a century after Dune, the novelty has worn off. At least, the super-detailed world-building should be allowed to lie fallow for a while.
Also, world-building has become a self-indulgence of some authors. It is a self-indulgence when a story that could unfold in 350 pages unfolds in 500 due to the inclusion of unnecessary background. I once flipped through a fantasy novel that described mourning rituals at funerals in excruciating detail. It was utterly irrelevant to the story. There is something almost masturbatory about it. It is especially pitiful when the author obviously thought, “By God, I spent 100 hours fleshing out this world, and I am damn well going to get some use out of that 100 hours, so I’m going to shoehorn in the names of all 68 of my fictional religion’s deities if it kills me!”
In constructing my fantasy setting I could have dumped a kiloton of material from my area of expertise, which is relevant for world-building, into the novel. But why? It would hurt the pacing and really, would just be me showing off.
There is a venerable notion that “Human beings live by the stories they tell.” You have never heard “Human beings live by the fictional elf languages they create.” There is a reason for this.
If I’ve done my job the way I wanted to, I grab you by the hair and take you on a divebomb from the front cover to the back cover. You barely remember to breathe or blink, let alone be detained by the heroine’s genealogy.