I would disagree with saying not to “learn” HTML; I also disagree with the lack of emphasis on learning CSS.
I understand what you mean by you’ll learn by doing it. But semantic HTML is SO important and learning by doing without understanding the meaning of what you’re doing misses the point of semantic markup. This is not to mention the importance of the box model and how difficult it can be to understand it when you’re first starting out.
With CSS, yeah you can learn Sass or pick things up here and there, but to truly understand CSS you have to dive deep inside the cascade and how specificity works.
Reading through the W3 documentation can be helpful, but when someone is just starting out or just getting their feet wet with development it isn’t a good place to learn the concepts from. On a final note, I venture to say that many of these other things that you say are opinions. While every developer has their opinions on how to develop properly, I don’t think telling people to steer clear of one library or use one framework over another is good practice when educating. We should be telling people to dive as deep as possible inside of these topics and learn the problems instead of just learning the solutions. When that’s done properly people will be able to make decisions about frameworks and libraries on their own and hopefully use the tool that best helps them get the job done.