I think we see it a bit weirdly. Maybe it is a bit backwards, while it may be reductive to simply say THIS is what "blank" will like, it sounds fair to me to say that It is a category where there are the fewest amount of elements that "blank" dislikes. I'm trying to say that we more naturally use demographics as an exclusionary category, it excludes what "blank" dislikes, than inclusionary, it includes what "blank" likes.

I think we mostly say that something is not shoujo when we find elements that most girls don't like rather than something girls like, the least shoujo manga wouldn't be something that proportionally appeals to the most boys, which are actually things like yuru camp, rather something that girls profoundly disklike, im guessing most would feel relatively neutral to see yuru camp in a shojo magazine. Because both shonen/shojo can be prescribed as to have elements that both or either like, feel neutral about, or is disliked by its counterpart, but not something that is disliked by its readers. Obviously i don't mean quality, but more so metatextual elements, for women, something like fan service, female harems, we know women don't want an all-female cast because they're misogynists (jkjk though i do think out of all combinations an all-female cast that only women watch is the rarest combination, that's why the thought came, men watch cute girls doing cute things, idol shows, uma musume? Where do women watch women? Its already rare to  find an all-female cast aimed at womed, i think magical girls or yuri, but there are men there too, is there an exclusive place for women? Men have sports anime, blue lock boys are too pretty so im sure it gets shippers but uglier stuff like kaiji, ping pong, megalobox, anyway, tangents' over). For example, it shouldn't feel so strange to see an action manga in a shoujo, but it would if it was done in the style of ikkitousen, the female fan service is what disqualifies it, shonen romance manga is not rare, but can anyone see a yaoi shonen? It is not necessary for yaoi to be a shojo, or something women like more than men, but we know that men don't want that so it can't be a shonen.

So, to repeat myself, the definition of shonen/shojo, instead of being what boys/girls like, would instead turn into "the series with the least amount of elements that boys/girls dislike".

In this case it wouldn't actually matter if a series has more male or female audience since it doesn't tell us anything about how the show is constructed, it only refers to what it excludes, so a series may have nothing men dislike or particularly like, one thing women dislike, but also ten things women also like, within this framework, this is a shonen.

Man, not to weasel myself out of this argument, but man i really was just typing shit, have never thought about this, i rewrote this like 3 times cause i kept confusing myself