[JamesBarney]

This doesn't apply to javascript as much, but might again one day.

But yes, spending my weekends learning a new language and library is not a feature.

I'd much prefer to spend my off time learning more about my target users, how to better manage a team, or the legal regulations surrounding the domain I'm writing code in, or just hitting the gym...

Not to mention as soon as I add a new language to our project stack that means every current dev has to learn a new technology, our build pipeline becomes more complex, we need a second set of coding guidelines, and finding new devs becomes more difficult because they'll need to know 2 languages instead of one or we have to increase the onboarding time for every future dev who roles onto the project.

I think it's uncommon that it's worthwhile to invest in a second language/tech stack on a real project.