1) Not statically typed 2) Not compiled 3) Super-cross-platform is cool, and not cool.
1: This one is obvious: it doesn't stop you from writing awesome code, but the type-hinting in Python still has a way to go. And what's type-hinting without #2?
2: You lose out a lot on a language that isn't compiled. It's nice to just be able to execute the code, but compiler warnings are awesome. Binaries are actually cool in a lot of circumstances.
3: It's good to know, in general, that you have the _ability_ to run on many systems. However, in the real world you still have to test extensively on all the platforms you want to run the code on, and you have to ensure the tech you're using is supported, of course.
Python is an awesome language for many, many things: but sometimes a language like C# or Go or Rust or.... makes more sense. Performance, statically typed, or pure-functional-programming is sometimes desired: these things are often harder in Python.
One thing Python has over many of its contemporaries is the _vast_ and helpful (fun) community. There's a million libraries (like from the JavaScript world) but unlike JS (in my experience, this is just because of the "newness" of the ecosystem) these libraries are very, very mature. And the tooling is actually really good, check out Conda for example!
I have a very different experience. JS libraries are typically fine. You usually have more than one option (because there's more than one type of nail). Libraries are smaller (Unix philosophy), so if it hasn't had a commit in 6 years it was probably complete anyways and loss of backwards/forwards compatibility is nearly never an issue. Python libraries always exclusively support the version of python you're not using (2 or 3) and are abandoned except for the really popular ones like numpy, django, flask, etc.
C# has static types, far better tooling, and is generally more maintainable. Go and C++ are way faster. Node has the benefit of allowing you to (share) code in the same language on the frontend and the backend. Every other language has "not having to deal with a broken inheritance model that makes me pass `self` around everywhere" and "doesn't silently turn things into tuples when I add an extra comma somewhere".
I will say that Python is one of the easiest backend languages to throw new people into and have them contributing quickly - but I think the gap has narrowed substantially recently. JavaScript has become so pervasive that Node might actually have the advantage now.