JS shiny new culture doesn't really exist on the back end (and even front end js has calmed down in recent years). Express.js, the go-to framework 7 years ago, is still the go-to framework on Node today.

Node and Mongo are at this point "boring tech". Their limitations and trade-offs are well known, their benefits are also well-established, and their APIs and tooling have matured.

Then there is also the fact that JS is actually a pretty great language if you know how to avoid the footguns. Granted that's not always easy, but it's a language with lexical closures and easy and familiar syntax, it's also very expressive and has a vast ecosystem supporting it. And you can even add the typescript compiler on top if you want compile-time type-checking.

It's also async out of the box, and while that doesn't solve all problems, it scales surprisingly well with no performance tuning whatsoever, it even has decent asynchronous primitives that make it easier to write correct code.

Give me a break.