Well, there are a couple things going on here. First is the blog post, which I can't really make sense of. It's 12,000 words on how to navigate high school without a single reference or citation. No evidence is presented whatsoever to support any of the assertions made. It purports to be a guide for 14 year olds but is written in a manner and published in a medium that is not accessible for 14 year olds; not many 14 year olds are reading 36 pages worth of blogs on substack. The author doesn't seem to teach 14 year olds or teach at all. He does not seem to have done any research for the post -- he hasn't spoken to any 14 year olds, or anyone else who has spoken to or teaches them for that matter. Paul Graham gets a quote though.
So really, I'm left to assume that this is just a letter from the author to his past self. That's how this reads to me.
As for the concrete advice you list, this is exactly what I'm talking about. Saying something like "get a computer" or "make a thing" will play great here on HN. But this is not advice 14 year olds want or need. Kids are creating things all the time. You do not have to tell them to create things. In fact, telling a 14 year old that they need to get a computer to before they can produce shows a distinct lack of understanding of how 14 year old express themselves creatively. Most of the advice in that section is focused on how to find a cheap computer, not how to create anything.
If you actually listen to the problems kids have today, it's not that they have a lack of creative outlets. The problems they are facing revolve around managing mental health issues, and there's not a single word about that in all the 12,000+ written.
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The other thing going on is the generic HN discussion on education the blog post has catalyzed. The blog post doesn't really touch on the discussion happening here, so it's kind of separate, but still related. Here on HN, the discussion often revolves around the Big Important Feelings posters have about the education system. You're right, there are problems, but they are rarely identified here. The solutions offered therefore often aim to solve the wrong problems.
For example, a lot of HN posters have a problem with the number of administrators employed at universities, and they even like to cite a ratio of admin to students or admin to faculty. Then they say "They ratio is too high! Fire the administrators!"
This is a classic example of Chesterton's Fence. Firing the administrators and hiring more faculty seems like a great idea from the perspective of the student, who interacts with faculty and not administrators. But from my perspective as a member of the faculty, I would not want this at all and it would make my work and the work of my students harder (for many reasons I have articulated in previous comments if you're interested in those).
For the HN crowd, this is like saying "The computer is running too many processes. It looks like a lot of those are daemons and system processes, so let's get rid of the operating system to free up resources. That way we can run more programs, because after all, that's the point of the computer." The average HN poster will immediately see 100 reasons why that's a bad idea in a computer system, but then go to advocate for something very similar in principle when it comes to the education system.