A big problem with a lot of fantasy and sci-fi worlds

You have a world with magic, alien technology, fairy dust, or whatever and then just assume modern capitalism. That is the number one problem that I have with science fiction or fantasy. You can create an entire fictional universe but then act as if the economics don't change. Like seriously the worst culprit of this that I can think of is Star Trek canonically everyone is perfectly happy with no money, no poverty and endless energy but its also a capitalist society. The issue is worlds don't work like that and that approach to world-building creates a world that is inconsistent and unrealistic. <br><br>When creating a world for a story just remember your economics might change, your world is inconsistent if they don't, and that it's the basic way that a world works; so don't forget it.