My teacherly anecdata (from about a decade of teaching) led me to think (in no particular order):
* Anxiety is way more prevalent and central to teen experience than most people realize. Definitely more so than I saw when I was a kid. You could say we use the language of mental health and anxiety to conceptualize experience more these days, and that's true to a degree, but it doesn't fully account for the prevalence or centrality.
* Social media is absolutely an amplifier of the problem. You can really just ask a kid -- they're often very self-aware about it. Many will say something like, "Yeah, I hate it, but you have to be there" or "I hate it but I'm obsessed with it."
* Further to the last point, kids are often a lot smarter about social media than we tend to give them credit for (and often a lot smarter about it than adults). Many are good at compartmentalizing online experience onto different platforms and different public or private or anonymous or real-name accounts -- since they've grown up with it, they've had more impetus to develop adaptive mechanisms. A lot of them create relatively private or close-knit digital spaces to retreat to when the big screaming public square gets overwhelming.
My own kid's a toddler, and I definitely worry about what all of this will look like for him. I want to expose him to technology and teach him to use and understand it, but at this point I'm super leery of exposing him to YouTube/anything with a whiff of social media any time in the foreseeable future.
On HN that's likely to be a popular opinion, given how many members here probably work in social media corporations.
I have lots of experience looking after relatives' kids in the UK and your points don't apply at all to them.
It's anecdata vs anecdata, but yours doesn't refute the article, and given your opinion may well suit HN biases well (we don't want to think of our work as causing mental illness) then I think the top voted comment needs a stronger counter argument than "my kids are like this".
It's not certain, but it looks pretty damn likely that social media has caused a dramatic increase in mental health problems amongst kids.
Maybe teachers could contribute something here with their experience? Parents see such a tiny sample size but teachers see 1000s of kids over a few years.