Earlier quoted context omitted.
Why is it a terrible advice?
Because programming != web programming, and sure as hell HTML/CSS is not programming. About javascript(vanilla js), nobody even wants touch it anymore. Almost anybody who interacts with javascript code does it with a 5 foot stick(coffescript, clojurescript), and/or behind huge frameworks that protects you from its perils. Something that is more usable and understandable in its barebones state like python makes more s…
There is a huge amount of tooling these days and specially the Node.js community and ecosystem are flourishing. Code coverage, static analysis, test frameworks for every use case imaginable, you name it.
Coffeescript and its brethren are a "solution" for people who are not interested in JavaScript and don't care about performance / maintainability in the long term. The additional compile step and the resulting problems with not being able to know exactly what it ends up generating become a huge burden in the long run. If you're really good in JS, you know what we'll be JIT'ted and what not, just like a really good C++ developer knows what the compiler will eventually optimize away and what not.
Seriously, building your cool, new library in is like writing the latest addition to Boost in C89. Nobody wants to depend on it in the long run.
From what I have seen, the people who are mainly using things like Coffeescript are coming from Ruby or Python and want their cool-aid back.
If you don't want to learn a language, don't use it and if that means you won't be able to do stuff on the web, well I'm totally fine with that. I've seen enough code that looked like a J2EE developer just started coding C the other day.