[benrutter]

I suppose that's true - but then I would suggest that type systems are (at least to some extent) the application of category theory.

It's hard to see how learning about Hindley-Milner type inference isn't academic type theory (which I'd argue is a category theory subfield) but applying Hindley-Milner type inference is clearly practical and related to producing technology.

I'm not saying all branches of category theory have a section that relates to directly producing technology, but I'd definitely argue that some do.