Fantasy. It's the easiest to write out cop outs if you've written yourself into a corner, but also if you're really into worldbuilding, you could probably do something complicated and wonderful.
Systems are the most common nowadays, but because its a fantasy world, you could use multiple ways of powerscaling, such as cultivation styling, or perhaps something more grounded like circles, or do all of them, because its a fantasy world and your rules are your rules to make.
Like stands from jojo are total fantasy, and you see the mileage that's been made out of that.
And on a darker note, you can definitely do some more twisted things in fantasy if you're so inclined, like relations between humans and I dunno dragons, or werewolves and orcs. Anything you can imagine.
I think smut in fantasy can definitely go places if you're willing to go down that path.I mean, off the top of my head, omegaverse, futanari, tentacles, non human creatures, aliens, elves, werewolves, orcs, etc etc. Half of that can definitely also be done in the scifi genere, but I find that scifi and fantasy often go hand in hand.