I'm seeing a lot of commentary that basically complains that category theory isn't useful. Like most topics in programming, it's useful for some things and not others, so YMMV. The parts of the programming discipline that are truly useful to all programmers are pretty much all learned at the beginning of one's career, or are really difficult to teach and must be learned by participating over time. The fact that you haven't found something useful doesn't mean it's useless in general, since it could just be too specialized to apply to your domain.

As a professional programmer, I personally can say that I have found category theory to be at least occasionally useful in my work, and for me it was worth knowing for that. But I've also studied a lot of math, so it wasn't a big leap out of my comfort zone to learn about it. Like I said, YMMV.