First thing's first, what I've typed below is all based on first-hand experience, which might be not representative of the general population, but probably not that far from how these kids who kill themselves feel.

First thing being that's being done wrong by parents is not treating their children like adults. The culmination of such treatment comes when the child gets separated from their parents, for example by going to college, and starts doing stuff like drinking/smoking/doing drugs/what else not because there are no parents present to punish him for it. Problem is that the child's subconscious thinks that the bad thing happening to him because of, for example, smoking, is not lung cancer and what not, but the punishment from his parents, so when they are not there to do the punishment, there is nothing wrong with doing all that stuff. In general, not letting children to make decisions and then deal with the consequences on their own leads to a population of people who are unable to think for themselves and who, while they have been told what's good or bad, haven't internalized that knowledge, as there is no opportunity to do so. You know, brain is kind of like a muscle, you have to train it when it's not really needed for it to be capable when it is. Actually Lois Rossman has quite a bit of parental advice that seems decent to me.
There is also a great emotional disconnect between the parents and their children. At least the message I've got from my parents is that I shouldn't even bother talking to them as there is a lack of even basic effort to try to understand what I'm trying to tell them. Not trying to blame anyone here, feeling exhausted after a workday is a thing but maybe considering not having children if you're unable to treat them properly is also a thing.
Honestly, I think dropping fertility is a good thing, as being more conscious about raising children is at least partially the reason, and that's a good thing.

Then school inevitably comes. You honestly can't expect an underpaid overworked teacher to manage 30 children in a class, there is just too much stuff going on. But, because teachers are underpaid and overworked, it is a low prestige profession so if things don't change, the problem isn't going to solve itself. Then there is the learning process. Problem is, in school people don't learn, they are being schooled, and then there is some learning happening as a secondary on the side. Problem with learning while being schooled usually is that the pace is way different and there is a ton of unnecessary extras. Here are couple of examples:

My English teacher would accept essays and other stuff that are typed, not written by hand, so what I would do is type them first, then just write down what I've typed. Why the extra step? Could be beneficial to go through the material another time and what not, but that could be done without spending the time and effort on writing it all down. At least in the professional environment, everything is being done digitally these days, so an all-digital workflow clearly works.

Maths homework was probably worst of them all because of how much of it accomplished so little. It is very much repetition based, so a lot of the time the task you're given a set of 10 identical problems, just with different inputs in them. That way by the fifth one, it takes a second to solve it and a minute to write down the solution, and there are 5 more like this ahead. That way, there is just muscle memory being built for solving that one problem, and exactly nothing is happening to the understanding of the subject, broader understanding of mathematics, creative thinking and problem solving, arguably very much needed skills in real life situations. In general, there are very little 'reality checks' that might indicate a problem a person has but himself is unaware of.

Yeah, you better remember things by writing them down and all that, there are way better ways to do all this though. From personal experience, I've learned much more and much quicker from actually doing projects which required the knowledge I've needed. Knowledge retention is also much better and you actually have something material to show after the thing.
Homework itself, in the form we have it now, is clearly damaging to relationships with children and their parents in general, as parents tend to care about things being done more than the well-being of the child. Results of that are genuinely horrific at times. Also there is that old text about a guy being unable to learn anything from a his professor's lecture, but understanding things immediately after reading part of a book that professor was referring to in his lecture. I'd say exchanging lectures for books and using professor's time for one on one discussion if there is a problem with understanding it's contents would be a much better use of everyone's time.
What I mean by all this is that school is laborious without need, or at least feels so, damaging to relationships, concentrated on remembering stuff and not actually acquiring any useful skills and all that.

Then there are people at school
Honestly, would feel good if people weren't called circle-jerks in class by the professor, who is angry (more correct term would be salty) that no one is doing their grad project with him, which happened because he calls people circle-jerks in class. Would feel good if the professor actually paid attention to my project and didn't ask, what that circuit drawing has to do with it, while that exact drawing has been basically copied one to one into the overall project schematic. Both happened the other week. This assumption that teacher is this unquestionable all-knowing figure of authority is very ill-minded, and overall power dynamics are sometimes very problematic in academia. Though younger teachers are much, much better.
Then there are your peers. Everyone is trying to one-up each other and being left alone to do your thing is not really an option, probably partially because of this built-up grudge, which happens for the reason I have described above. Interest circles are largely dissolved and at least in my experience, connecting to people without directly being introduced to them by someone is increasingly difficult. Platforms like tinder are considered, speaking in gen-z terms, 'cringe' (I'd say tinder is very exploitative with it's business model, but that's not the problem being addressed). Besides that, with all the extra-curriculums, homework and general attitude by parents to make their kids busy, there is not that much time to go outside and do things that you actually enjoy, or finding such things.
So there is basically pressure at school from peers and teachers, pressure from parents at home and being constantly busy doing stuff which prevents you from thinking about your issues and potentially dealing with them. There is a big need for a place of some relief, and social media and the internet tend to fill that role.

Well, if we're talking about social media here, there is a lot wrong with them also. I'd say these days there is a tendency for relationships to become parasocial, like 'I follow you on socials, you follow me on socials, but we don't actually talk to each other directly', so what would have been a two-way conversation between two people turns into two one-way ones. Then, exposure is spread very unevenly. Some people tend to get lots of attention and generally are popular, while some get none. This attention is of very varying quality, but getting it is still a message of acceptance by society, while getting none sends you a message that you are rejected. Texting people on social media out of the blue is generally a bad idea, because most people who do that are scammers, advertisers and people trying to get you to distribute drugs for money and so there is a tendency to treat strangers like you would treat someone spamming your email. This lack of attention basically sends people a message that they are not welcome/needed/wanted/desired in general. After some time in this circle the person starts to feel that it's not like they're in a bad situation, but that he himself is bad in some way.
What they learn in the end is that there is no place for them in the society, and that other people don't care about their situation.

The stuff above might be not factually correct but that's how troubled people experience things, from which they learn their apparent place in society.

Returning to the girls taking pictures and posting them to IG/TikTok are probably fine just fine. Actual people who are in danger are not doing all this stuff and are basically invisible cause they just bottle up all the stress, and after some time they may be unable to deal with it because they never had a chance to learn to. There is also lack of prospects in life (ever increasing rent, working minimum wage for most of your life and other stuff) and what not. When things add up, we see statistics like this.

Personally, I don't know, if generations prior had it easier or something, but I don't see these lowering any time soon, and actually was kinda wondering why haven't they gone up before