I mostly agree, however it does seem to make some sense to dive deep into one ecosystem, instead of learning & keeping up with two. (Let's not pretend that Javascript is the only one advancing--Django of a few years ago is not compatible with Django of today, as one other example).

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.

Would you mind elaborating on some of those practices (specifically, the problems that made working on the first codebase abhorrent)?

healthy competition is robust and tested. A short fade that's gonna be abandoned within a year or so doesn't quality as healthy competition.