from the link:

CoffeeScript’s intent, however, was never to be a superset of JavaScript. One of the guiding principles of CoffeeScript has been simplicity: not just removing JavaScript’s “bad parts,” but providing a cleaner, terser syntax that uses less punctuation and enforces indentation, to make code easier to read and reason about. Increased clarity leads to increased quality, and fewer bugs. This benefit of CoffeeScript remains, even in an ES2015+ world.

so, it's not really about "CoffeeScript's functionality" but more it's "style".

Truth is, though, if you're going to pay the transpilation tax (and it's lower than many still seem to think), there's just better options: TypeScript, Flow, ClojureScript, PureScript. A nicer syntax was never that interesting.

Yep I agree. Coffee script's terse nature makes it great to write readable tests.

Yes, I still use it when I'm in Rails. Even in new rails apps it's easier to use coffeescript than babel. The newer sprockets beta still isn't reliable enough.

Ruby programmers, mostly. Same as it ever was.