here is my best worldbuilding tip for authors who want a thick, dense world with real verisimilitude. i stole it from gundam and now i'm giving it to you.
lesser worldbuilders start from what they want the story to mean or contain. i am here to give you formal permission to reverse that: start from what you want to exist. "i want to write a science fiction melodrama about the ethics of teleportation" - wrong. "i want teleporters" - yes!!
the failure mode comes in two disguises, which is why this advice is hard to give. disguise one is theme-first: you decide the thesis and then build a world backwards to prop it up, and readers can smell a rigged demo. disguise two is trope-first: "there are kamen riders, and evil organizations, and they make robot monsters, and it's themed around such-and-such" - you've imported the genre's conclusions (evil orgs! kaijin!) without the causes that produce them, so nothing load-bears. same crime, different trenchcoat: fixing the outputs.
instead: find the stupidest, most childish version of the idea you're most excited about. "what if kamen riders were real." then work backwards and invent the FEWEST possible things that can justifiably load-bear - "why would a technology exist that lets one person become the functional equivalent of a tank, and how, specifically, does it print its armor so quickly?" establish your minovsky particle. then roll the tape forward.
and here's the part everyone skips: you have to keep the consequences you didn't ask for. that's the whole trick. your themes should be exhaust, not fuel - if you roll the tape honestly, the story you were trying to order off a menu shows up on its own, plus three better ones you'd never have thought to want. verisimilitude is just the reader failing to find the seam where you cheated. only tell one lie and there's only one seam.
