That goes for themes too. Some issues can be touched on -- just as some details can , but others need to be grappled with, or ignored entirely.
For instance, always-evil types. Whether ogres and trolls and the like in fairy tales, or orcs in fantasy novels, or supervillains (whether by descent or by power -- the guy with necromantic powers is always evil). You can just run with it. Or you can grapple with the issue, having a young supervillain type complain that he's judged before his crime, and that heroes are not only presumed innocent, but irrebutably presumed -- and historical stories of how this vilain or that was not villainous until pushed into it, or crimes heroes committed, and moral wrestling on both sides. Complaining that supervillains are presumed guilty without showing they are sometimes innocent is incoherence,
(Though, of course, with supervillains you could justify the powers by having their source be personality. Destructive powers being a strong sign of destructive personality, beneficient ones of beneficiant people. One wonders if the powers would leave by character change.)