Absolutely there's a spectrum and I certainly don't fully understand the full set of category theoretic structures (I'm slowly trying to learn, but.. its slow going). I just think that monads as programming constructs are quite simple. I don't doubt that in a full mathematical context there is a hell of a lot more to them and the mathematical reasoning behind how they work is surely beyond my understanding, but from a how they work, how to use them, how they interact with the language and what they enable you to do point of view, they aren't difficult at all.