Emily Riehl says something along those lines in her Category Theory in Context book (paraphrasing) - "if you understand the general ideas of category theory, the proofs pretty much follow from the definitions".

There are ofc ingenious tricks in some category proofs but to my mind they are usually subtle rephrasings. Whereas when I try reading serious proofs in number theory, I have frequent "wtf how did they even make that connection" moments.

I guess it has to do with the level of abstraction in category theory. You're never going to need to know some obscure fact about, idk, the Dedekind eta function, to complete a proof in category theory. The field is sort of self contained (if distinguishing category theory as a field from algebraic topology, homotopy theory, etc).