> This is a common counter-argument. It is a true statement. And, in the nicest possible way, it is also completely missing the point.

Yes, kind of.

> When you're playing with cute mathematical code and almost everything is written in terms of totally generic types, it's cute that you get free theorems and automatic derivations of some basic functions and all that stuff.

It's not only "cute" as you so reductively put it. There are real world benefits.

> However, in the real world, 99% of the time we work with concrete types to get concrete work done, and there are going to be many possible implementations of a function of type Int -> Int, or MyDataStructure -> MyDataStructure -> MyDataStructure, or SomeWrapper SomeType -> (SomeType -> SomeOtherType) -> (SomeType -> SomeOtherType) -> SomeWrapper SomeOtherType. This remains true notwithstanding the possibility that some of that cute generic code was used to implement various small parts of the function you actually care about if you dig down far enough.

That presumes an arguably wrong method of developing software that needlessly eschews understanding and correctness confused for superior economic choices, finally resulting in "real world programming".