I'd say it is in fact a familiar abstraction (as the "You Could Have Invented Monads" article shows) that's presented in an unfamiliar way with unfamiliar synta

I'd say it is in fact a familiar abstraction (as the "You Could Have Invented Monads" article shows) that's presented in an unfamiliar way with unfamiliar syntax. Taking something you already understand intuitively and learning to express it in a new formal framework (like much of Haskell) is often harder than learning something brand new in a formal model and slowly developing an intuition for it (like much of physics). Sometimes gaining a formal understanding enriches your intuition and vice versa, but I haven't experienced anything like that with Haskell so far.