Yes. You use std::function when you don't want every function/structure, that accepts a function as an argument, to be infected with templates, and instead be a plain function/structure. Thanks to that:

* there will be only one instance of it;

* you'll be able to export such a function in public interface of a dynamic library without exposing its source code in a header file;

* compilation will be faster, because the compiler won't have to instantiate N different versions of a template;

* you'll see fewer scary template errors.

Your life as a human being will be happier.

Of course there are better alternatives to std::function in the wild, but the general idea remains.

std::invokable will just make working with templates nicer. But not working with templates is nicer still.

EDIT: You can think of std::function as the LSP inside C++. There is a famous matrix where rows are for editors, and columns are for languages. In case of std::function rows are functions accepting functions as arguments, and columns are functions passed as function arguments. The matrix represents template instantiations, when you use templates. By using std::function you avoid the matrix and instead have just two vectors of length N and M, if the matrix was NxM (N functions accepting functions as arguments, M functions passed as arguments).