I could not disagree more. Rapidly picking up any language is simply not possible (unless you're a genious). Because the language is not just the syntax; It's its history and evolution, design choices, documentation (or lack thereof), community (both kindness/aproachability and responsiveness), leadership, etc. It takes time. Which sometimes, as an employer, I'm not willing to invest in. Because money.

Plus you've somehow managed to state that JS developers are not decent enough.