I love category theory, but I feel that its penetration of JavaScript or most other languages doesn't (and likely won't) get much farther than monads and functors. Many people who use functional languages don't even know about applicatives, even though monads can be viewed as a specialization them.
If you're thinking about new programming paradigms I think the theory behind CT versions is worth knowing, but if most of your monads are maybes or lists it'll be of little practical value.
> but if most of your monads are maybes or lists it'll be of little practical value.
I think even this is maybe too much: if all you use are monads and functors, then it's easy enough to learn monads and functors on their own, without any "real" category theory.
If you're thinking about new programming paradigms I think the theory behind CT versions is worth knowing, but if most of your monads are maybes or lists it'll be of little practical value.