I guess it's only / mostly Gamefreak (or Nintendon't)'s fault when they say Pokémon is for kids, because unfortunately they insist on both marketing and showcasing the franchise as "limited to children", *and* designing the games to promote merchandising stuff. When, like, there's not really need to? There's nothing non-adult about desiring the
life-size Arcanine plush, but unfortunately the main franchise promotion is designed to make it look that this is something that
only children, or immature people, should desire.
However, once you get outside of the mainline games and the mainline anime, Pokémon has quite a wide offering for youg adults and in general for people who have had gaming and media experience for over a decade. It has an official fighting game, a Witcher / Zelda / whatever "open-world meme" game, a set of non-serial movies to collect, a trading card game where pulling off some serious
Yu Gi Oh narm when sending your opponents to the
Shadow Realm Lost Zone wouldn't feel out of place, and lots of stuff like that.
Heck, one could make the argument that if TPCi made a
little more effort they could easily merchandise adulting stuff such as Rotom laptop (or desktop!) cases, official Mach / Aero bikes (for competition, even!) and the
one thing from Pokémon that any past-young adult really needs:
AR-assisted VS Seeker. Seriously, if Pokémon launched that everyone would forget the Google spy glassses in an instant.
And, let's be real, all this "childwashing" that Nintendon't does with the franchise makes zero sense when the games already show Pokédex entries suggesting quite the things, be it violence, sex, or simply "nature is not nice" (see: every G7 Mega evolution dex entry). Come on GF, Pokémon
dating sim / romancing VN when? And I don't mean featuring the
human females, they're overrated.
Oh well.
At least we have the creative fandom. There's pretty good non-childish stuff outta there such as "One Piece but with Pokémon" or "Blade Runner but with Pokémon".