Earlier quoted context omitted.
Really? The latter was immediately useful to lots of people which is motivating, and it had a nice smooth learning curve (html -> js -> php -> databases -> apps -> backend). Learning HTML is the first step to learning how to make full blown apps. Making a browser at 17 is like trying to climb Everest as your first hike. The expected outcome is burnout and demotivating failure. At best you'll learn some C++ or Rust. 1…
Anecdotally, I think it's great advice. I contributed to a browser engine around that age (KHTML, which later became WebKit and Blink), and while I don't work in browsers right now, much of that knowledge, mindset and of course the professional network have done much to shape my life. And a fairly successful career, for that matter.
If teenagers could make small contributions to LLMs via open source then sure, go for it. Optimizing llama.cpp or similar would be a good learning project that might later get you good work via social networks. Contributing to open source is how I got started too.
Unfortunately, training LLMs isn't something that fits well to open source open collaboration. Inferencing codebases are better.