it COULD be mainstream but only certain kinds.

Like my hero academia, naruto, one piece, and movies like Your Name, Koe no Katachi. That kind is totally mainstream ready.

The other kind of anime which pander to otaku.... is usually based on perversions if you will. Like. Think about how normal it is for people to talk about about best girl, waifu, whenever they think about anime. That's because anime sells sex you could say. The base girl in these type of show is usually some kind of highschool or younger girl. If it becomes too mainstream then it could change to where all girls are 18+ yo college girls or something. That would suck imo. But it could happen if the mainstream money like from netflix/CR/Amazon/etc starts to become greater from the amount from japanese otaku.... which could happen just look how poorly Hinako note sold. And from the 4chan thread the other day seems most the current running shows are in danger of flopping as well... otaku money is becoming less reliable whereas western money is growing. Well not just western money also other places like china, there was a chinese anime in japan this season, or last season, i believe.