Python

Like anything else, these sorts if issues are rather murky and are directly impacted by the user's competence in the tools.

Does python have obvious overhead issues? Yes.

Does Python have to be super inefficient? No.

Take basic set operations, for example. Do it manually in the language and it will be dog slow. Do it using the set class? You are leveraging the speed of the underlying C implementation.

E.g., In competitive programming eventually need C or Java, but a strong Python user can move the bar significantly in terms of how many problems are possible with Python.

If you don't want mutability you have to go to a pure functional language like Haskell, but then you have to copy a big list every time you make a change. There are ways to optimize copying by secretly sharing data behind the scene but you pay a performance price in some way.

I don't believe this to be the case. The immutability is precisely why efficient structural sharing is possible without screwing up other data structures. And for standard stuff, it is actually happening behind the scenes already.

You see similar claims about recursion in general, but those claims are often so broad that they don't hold water. I mean, yea, if your language sucks at optimizing recursion it isn't going to be a pleasant experience, but tail call elimination, lazy evaluation, etc. mean you can write some really awesome and efficient code.

I think the bigger problem is that it takes a lot of time to internalize what is going on under the hood when you make a call or initialize a data structure.