[Koshkin]

Historically, Category Theory was developed to formalize and better understand some deep methods used in mathematics. Like much of mathematics, it "automated" some types of reasoning, opening possibilities that did not (practically) exist before. There are some areas today that cannot even be properly understood without thinking in categorical terms.

[bubblyworld]

I would like to second this take, as someone who found it very useful while writing up my masters (in logic). When you're working with objects that satisfy lots of universal laws (particularly algebras, logics, stuff like that) CT can be used to remove tons of "boilerplate" in your proofs for things that are basically trivial/routine but a pain to state and prove formally. As an example, imagine a construction where you extend the underlying language of some logic (like adding additional constant symbols in, for instance). Strictly speaking, to "transfer" results into this new logic you need to do a bunch of tedious proof to show that everything goes through the way you would expect. Category theory can make expressing and working with this class of thing (and many others) very expedient.

It's a bit like working in a framework that has great primitives for the stuff you do a lot. Like think dependency injection for constructing instances. Saves you tons of coding time in the long run.

Of course, this point of view is probably hard to appreciate from outside the priesthood =P.

[ogogmad]

Yes it did, except all of those examples where it convincingly helped were super-advanced, very hard to comprehend, and lacking in non-niche applications to CS or physics.

There is a category theory "school of thought" in certain subjects, but it's usually a speculative belief in the importance of category theory.

[bubblyworld]

Improving communication between experts in a niche discipline is also a value-add, in my opinion (and my experience, for whatever that's worth). There's no need for it to have mass appeal to be useful.