Superheroes weren’t intended for such a small demographic until recently. And making them appeal to adults who never outgrew superheroes is what’s holding back their potential to be greater.
One can write an adult superhero story without resorting to sex and violence though it’s harder to pull off because it involves not only restraint but awareness that nobody likes that.
Superhero cheesecake can be pretty redundant in the presence of actual pornography. It can trigger fetishes but superhero porn isn’t appealing to most people either.
I could be wrong about it. But superhero media increasingly preaches to a choir. Replace superhero with furry and you’d get something similar. Both of them involve incomprehensible tropes and fetishistic imagery and themes.
Similar things can be applied to anime. What’s alarming is that they appeal to niches so specific they’re obviously not meant for anybody else. It takes extraordinary awareness to realise this but some furries and superherofags have shot themselves in the foot, taking away any potential for world domination.