As someone who spent the first decade or so as an embedded software developer, I wanted to move into web based systems because its a "bigger world". I'm a couple of jobs into this bigger world now, and it just keeps getting bigger. I feel the need to keep my finger on the pulse of new tools and technologies, but I try to hold that in tension with the advice we get here to keep things simple, be pragmatic, don't adopt technologies or techniques just because google does. I've always fancied myself as a generalist, but this bigger world makes me feel a bit like Bilbo Baggins, "like butter spread over too much bread."
My point: I've been in both worlds and I feel more at sea working on internet based systems. I had more mastery over the embedded systems I worked on, than over the web based systems I work on now. So my experience is in support of the author's point that ...
"anyone with enough brains and patience to learn how to do any kind of computing is “smart enough” to learn things like this."
Moreover, I would suggest that the average full-stack web developer is probably over-qualified.