There's a difference between celebrating adolescent, nascent, "innocent" sexuality and youth and eroticizing prepubescent children.
I get wanting "juvenile" depictions of love taken out of the context of adult society and adult sexuality. As someone largely put off by what he sees as the motions and the structures of romance as an adult (or a lot of life in general as an adult), I completely get that. I get wanting depictions of amazing girls that are amazingly into you in a way that manages to both be "thirsty" and "pure." Sexuality is put off on the female characters: they come to you in varying cute/exciting costumes and with various endearing personality tells to express their love and their lust for the (loosely-defined) self-insert. If I can really get into the girl's character it is an incredibly cathartic and self-affirming experience.
This is a lot of what I look for in Japanese romantic content, juxtaposed against the western content I consume, which tends to be very dystopian and very cynical as I see it. Sex is often just a shocking event in a lot of western content, frequently depicted as largely random, bestial, and exceedingly disloyal (particularly on the part of men). There is a focus on our sexual "demons," so to speak, and as a person with a romantic bent, I find such content alienating and depressing. (Not that that is wholly a bad thing: those are the sorts of things I've grown up looking for in western content, when done well and with awareness).
I think it is problematic content--in the sense that it feeds fantasies about dream gendered relationships, which can feed the very frustration they are supposed to help alleviate and lead to toxic expectations of real world women--but it is also content, for which I think there should be room. I just think that it should be an examined space.
The thing is, you can have this obsession with idealized youth and idealized young love without having an obsession with prepubescent children. Japanese cultural products (and indeed much of the world) also have this obsession.
You can also have an interest in pre- (or proto-) sexual childhood love without mining it for content to titillate post-sexual love. This is also not uncommon. Love rooted in a common childhood experience is a popular theme.
It is the cross between digging as far as possible into the past and imbuing it with the desires of the present that are maximally inappropriate/disturbing.