I feel there is impedance mismatch between the mathematical category theory side and what is needed for programs. A case in point is the infamous complex diagram for the Lens library in Haskell. This is abstracting the notion of getters and setters to some extreme and is several hours of work to really fathom. Compare to Go where the tutorial does balanced tree comparisons as an intro example to coroutines, when the language gets out of your way I feel it is much nicer. Haskell is more of a playpen for PL ideas. Some of those ideas get promoted into the mainstream when shown to be very useful! So Haskell is very valuable in that sense but can be difficult to write code in. Especially if you want to use libraries that may use complex category theoretic libraries.
A case in point is the infamous complex diagram for the Lens library in Haskell.
That case is due to history and path-dependence. The theory and abstraction of the lens library was developed long after Haskell the language was designed. If Haskell were rebuilt today from the ground up with lens in mind you wouldn’t have that mess. Unfortunately, fixing it now would be too much of a breaking change.
It's also a common psychological pattern.. you go from fuzzy experience and semi defined patterns, later you see more rigorous and precise definitions but they make you confuse a bit and one day you get it fully. Math, haskell etc have a tendency to live in the latter stage.
