(I didn't, largely since I've never watched a single episode, but the psychic damage and whiplash of Wholesome Pony Show having said this line was too fuckn much for me)
EDIT: More replies than upbears now. It’s probably an official struggle session now (although most of it is that one person). One must imagine SisyFEWs happy.
You said it's related to Made in Abyss so I take it there's a lot of
factor too. 
It predates it, but it is similar in tone and grotesqueness. Although thinking about the full depth of the problems with Made in Abyss that I covered exhaustively in a post last night, FOE:PH isn't as bad. It's a gratuitous, edgy spectacle that handles problematic themes poorly, but it's merely making an exploitative spectacle of them while Made in Abyss is even worse. AFAIK most of the characters in Project Horizons are adults though, though I think there's some nonce stuff in there too.
I have no idea why you read it, but I assume it was something like this as a situation.
I compulsively consume problematic slop, and was even worse about it a decade ago when I was in the process of rebuilding my schema from the ground up after dismantling twenty years of calcified repression brainworms, which is around when I read part of the then-incomplete FOE:PH specifically because of its reputation. Made in Abyss has to be the only thing that's actually made me sick to watch, however. I can't emphasize enough how even the people who condemn it undersell just how vile it is; it's in a league of awful all of its own. Like I feel even my "Made in Abyss is the worst thing anyone has ever made" rant is too soft, because I couldn't stomach really dredging up the specifics.
From what I know about it, there's a blurry line between "presents and does not condone, and maybe didn't read the room and has hogs eating the slop now" to "presents and claims it does not condone and it's clear the makers are also the hogs."
I think there's generally three fuzzy categories problematic content can fall into in mainstream works: presents [bad thing] and condemns it, clearly establishing that it's bad; presents [bad thing] and shows that it's harmful but takes no overt stance, leaving the audience to infer for themselves that it's bad; and presents [bad thing] and really revels in how the spectacle of it being awful in a crass and gratuitous way.
Made in Abyss is a fourth category altogether: presents [the worst shit you'll ever see] and revels in it, and narratively treats it as normal and ok. It transcends the whole "showing things are bad vs making a crass spectacle" spectrum by becoming a de facto endorsement of what it's showing off.
Fuck, I really need to find something to take my mind of this and hope the brain poisoning from engaging with it wears off soon.
you mentioned watching utena, did you ever finish it? it handles a lot of the stuff that you described in made in abyss but like. it is good at condemning the way children are groomed and exploited in patriarchal societies, and never sexualizes them, and has all the characters grow and change over time
I have not gotten back to it yet, I'm still working my way through Sailor Moon and nearly through the third season.
how is that? i remember the 3rd season being my favorite, but i'm a very different person now
sailor moon might be better at washing away the made in abyss, so that might be smart
It's ok. The earlier half of the season was better, I think, because Haruka and Michiro are more interesting characters when they're being people instead of standoffish edgelords without a fraction of the conviction they claim to have, and they get worse about doing that after the season's turning point. The fact that the story's being driven along by poor communication on all sides is also more frustrating than anything and brings the story down a bit - the back and forth between Haruka's "grr I'm so edgy and brooding, no one has my strength of conviction! I would sacrifice anyone and anything to save the world!" and Usagi's "Noooo that's bad actually!" just feels kind of hollow in the context of the main characters all literally dying in the first season and Usagi in particular having sacrificed her life no less than three times already by that point (well, I think she actually only died twice and the other time she just nearly died, but still). Chibiusa is also just an extremely grating character, though Usagi's character growth in starting to actually act like her mother is sweet and the one redeeming part of her inclusion in the story.
Aggretsuko is a good time and may work like brain bleach with a bit of cathartic rage.