I see where you're coming from, but I'm not sure this is as clear-cut as you think it is.
I started running other RPGs almost immediately after D&D, in like 1990 (AD&D 2E was 1989 for me), and I don't actually find it significantly harder to come up with what I need in terms of plot, place, people, concepts, drama and so on with other games than D&D. D&D actually is kind of demanding in that you need loot, you need maps (usually), you want a wide variety of monsters, enemy spellcasters are a severe PITA (as are spellbooks if they have them) and so on. I can make up SF adventures, particularly Star Wars-ish or cyberpunk-ish stuff very easily, like really really easily. Probably more easily than D&D. Likewise quite a wide selection of genres.
I don't find D&D-isms are universally helpful - I think they're actually a mixed bag, because some are more demanding than other genre stuff (again particularly loot/treasure/monsters/enemy magic/etc.). Overall because I know them really well it's not too bad, but I know from long experience that there easier things for me, personally, to do prep, than D&D, of any edition.
Superhero stuff is particularly a no-brainer if you have any pre-prepared villains. It writes itself, as they say. I literally can't think of anything easier to prep than Marvel FASERIP (excluding ultra-light improv games like "Roll for shoes" or whatever its called).