I like npm. For package management, I think npm is on par with bundler (ruby) and thus a bit better than pip. I like the ease of use of package.json scripts and find myself using them more and more. They feel lighter and easier to set up than the ruby equivalent (rake tasks, usually), although when you start doing fairly complex stuff (e.g., custom asset management), they can get a bit unwieldy.

As for the ecosystems, I find javascript is more in flux. It is more work to keep dependencies up to date or to decide what library to use when you need one, and I've had apps break on minor and patch updates to dependencies fairly often.

There is also a focus on small libraries that just do one thing. Nothing wrong with that, but the number of dependencies some projects have is a bit crazy.

If you work with Ruby or Python for web stuff, you inevitably end up using JS for the frontend, so it is certainly a reasonable choice to use Express as the server and go full Javascript.

And my company does that a fair amount, but when we need an app to do something more complicated than serve web pages and talk to the database, we end up moving over to flask/python to take advantage of python's better libraries (esp. for math/science/data stuff).

So, I still see some value in picking up python. Nothing wrong with any of the other languages though, and you can learn a lot from any language. Depends on your interests and needs really.