I read this interview with Alan Moore today, and it's pretty interesting how his criticism also applies strongly to anime and manga:
http://www.theguardian.com/books/2013/nov/22/alan-moore-comic-books-interview
I hate superheroes. I think they're abominations. They don't mean what they used to mean. They were originally in the hands of writers who would actively expand the imagination of their nine- to 13-year-old audience. That was completely what they were meant to do and they were doing it excellently. These days, superhero comics think the audience is certainly not nine to 13, it's nothing to do with them. It's an audience largely of 30-, 40-, 50-, 60-year old men, usually men. Someone came up with the term graphic novel. These readers latched on to it; they were simply interested in a way that could validate their continued love of Green Lantern or Spider-Man without appearing in some way emotionally subnormal. This is a significant rump of the superhero-addicted, mainstream-addicted audience. I don't think the superhero stands for anything good. I think it's a rather alarming sign if we've got audiences of adults going to see the Avengers movie and delighting in concepts and characters meant to entertain the 12-year-old boys of the 1950s.
Now, first off, we know that Alan Moore is a super hipster and an inane ass. The fact that he looks down on his own audience is kinda laughable, and he loves shitting on anything popular because he's well... a hipster (epic beard though). But having said that, there's a really interesting psychology here being discussed, which I think should not be waved away with "Lol Alan Moore".
It might not be a serious social problem that there are generations of manchildren now who continue to enjoy the childish things originally targeted at young children. But I think there is an interesting effect on industries in general when that happens because the demographic changes, and with that the expectation of content as well, but the core appeal of the product does not change.
In American comics this has led to more anti-heroes, dark heroes, and basically twisted versions of innocent characters created for kids now encountering and dealing with more violent and sexual storylines. For anime and manga though, what we're definitely seeing is that with more older audiences spending money in an industry originally intended for children, there is content which is more sexual and/or dark/violent, but they happen to characters and settings which are still relatable to kids - highschoolers, etc.
It's really pretty weird when you think about it, and certainly abnormal. I guess Moore has a point after all!