As a programmer and hobbyist math reader, I found category theory to be very unrewarding (and I gave up on it) because of the lack of interesting theorems and lemmas. My takeaway was that there's Yoneda lemma and really nothing interesting before you reach that. Like, CT describes a set of rules but very little emerges from those rules.
My complaint has nothing to do with whether CT is useful or practical. By contrast, abstract algebra can be taught (e.g., in Herstein's books) as pure abstraction (very dry and without presenting any real-world connections), but you reach Lagrange's theorem right away -- which is an simple-but-awesome result that will wake up your brain. You reach Cayley's theorem and others quickly, and each is more exciting that the last. And this is all while still in the realm of purely-abstract math.
My complaint has nothing to do with whether CT is useful or practical. By contrast, abstract algebra can be taught (e.g., in Herstein's books) as pure abstraction (very dry and without presenting any real-world connections), but you reach Lagrange's theorem right away -- which is an simple-but-awesome result that will wake up your brain. You reach Cayley's theorem and others quickly, and each is more exciting that the last. And this is all while still in the realm of purely-abstract math.