I find this topic fascinating but hard to start with.

Does anyone have any non-Haskell example of category theory? Something that shows why is useful with a use-case.

This series has some C++ examples alongside Haskell: https://bartoszmilewski.com/2014/10/28/category-theory-for-p... and acquirable as a PDF at https://github.com/hmemcpy/milewski-ctfp-pdf