Personally, I can't stand javascript, and why you'd ever elect to use it for backend/server side code mystifies me. So I don't use it (or work in web development), and couldn't care less about what platform the hip web devs deem acceptable.
I have always used python/ruby on the backend, and I prefer them, but I recently worked on a couple of javascript backend projects, and I found one abhorrent and the other quite pleasant.
As could probably be expected, the practices used to develop the latter were just better. (These were even done by the same developers, in large part, and the differences were mainly lessons learned).
Anyway, if you're already working in a javascript-heavy front-end like React, it doesn't seem like such a stretch to use it on the backend, too.