Floating out there in the general discourse are what seem to be two contradictory ideas of anime fans.
1) Anime is appealing increasingly to a smaller and more niche crowd of otaku, often through devices such as loads of fanservice or active use of moe. As such, the fanbase is becoming more and more a select group of adult men who grow older and smaller in number over time.
2) Anime fans are getting younger and younger, that anime is attracting a primarily female audience. Moreover, a lot of these young fans are not able to retain their fandom as they grow older. They hit a certain age and anime stops being their obsession.
So somehow you have a fandom that is both shrinking and growing larger, while the median age rises but also lowers or remains the same, and this is all being done with the same collective pool of works we call “anime.” On the surface, something doesn’t quite add up. The more I think about it though, the more I find this isn’t necessarily an irreconcilable contradiction. I mostly have impressions and hunches from observing anime and its fans, but I can think of some possibilities as to how these two concepts can co-exist.
It might be that some fans are longing for another period of anime, a self-defined golden age where anime was at its best. If it’s not simply a matter of nostalgia or specific tastes though, then it could be that these fans are not finding what they want in either side, the young and general, or the old and niche where they might have once been able to easily. So the anime fanbase may not necessarily be shrinking overall, but the demographic ratios may be shifting in a way that’s troubling to some. This one does not necessarily have any flaws, but it seems more to be a mix-up of personal desire for general trends.
Another possibility is that the effects of anime’s move towards extremes in its fanbase cannot be felt immediately and that it will take some number of years to really see the fallout. Perhaps it would be the age at which the current otaku base starts to literally die off, much like some of the criticism surrounding the current state of American superhero comics. This one doesn’t quite feel right through, and I can’t put my finger on why.
Similarly, while the younger fanbase is increasing, they are finding their access to anime through inexpensive means, be it through outright piracy or simply watching things streaming. “The surest” way at the moment to make reliable profit is to hit the collection/merchandise-obsessed otaku, hence all of the light novel adaptations. The amount of money being generated by anime is not what it used to be and may never be at that level ever again, even if there are new fans.
Overall, I’m not really sure. These are incomplete thoughts and I don’t think I’m going to be reaching a solid conclusion any time soon. I’d like to hear other people’s thoughts.