A lot of Shonen are abridging the training arcs (ex: Demon Slayer, Mob Psycho skipped the training arcs).
It seems to be some new hypermodern kind of storytelling. Turns out that the "Training arc" really isn't needed. But even something as old as "Full Metal Alchemist" never really had a major training arc.
But Demon Slayer is popular because it was written by a woman and drawn kind of shoujo-y.
(Jump, which has no women working for it and never has, doesn't actually realize this. They think it's popular because it's got demons and stuff, so they approved a bunch of mystical setting comics to follow it up… like Ayakashi Triangle… clearly women are going to love that one.)
Hiromu Arakawa (Full Metal Alchemist) is a woman. EDIT: Oh, wow, that's not a "Jump" manga. Huh, well TIL... so your point stands.
CLAMP also made a scene back in the 90s / 00s by emphasizing the shear number of women in their circle. They made all sorts of manga too across all genres... even dabbling into erotica. Cardcaptor Sakura, Chobits, xxxHolic, Rayearth, the character designs for Code Geass, etc. etc.
IIRC, Cowboy Bebop's script was also written by a woman. Etc. etc. I do hear that Japan is pretty bad when it comes to gender issues but I'm really not super into the culture believe it or not (I do like Anime/Manga, but I understand that's just a subset of the culture).
Manga authors don’t work “for” Jump, they’re contractors and keep ownership of their work. That’s why the One Piece guy is rich unlike any of the actual artists behind the MCU.
The manga publishers work by having editors keep the creators on track every week and canceling work that loses too many readers.
Totally random, but I literally just read the scene in When supernatural battles became commonplace where they have this conversation almost word for word...
Wait a sec...
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I think the cool thing about anime is that they've managed to discover that males like romance too (and girls also like fighting).
So action-oriented Shojo, like Precure (or DNAngel, or Sailor Moon) is big. But so are Romantic Shonen.
Most shonen are about fighting, most shojo are about romance though. So the stereotype holds for sure.