you're missing the argument i made. i didn't say category theory isn't useful or powerful. i said it isn't replacing set theory in practice.

you can make it through the lion's share of a ph.d. in math without using category theory, but you'll use set theory ubiquitously up until you start doing categorical things. of course category theory is a powerful relator. but it is awkward for when simple sets do just fine. loring tu's manifolds book is a good example of this. set theory is used throughout with categorical concepts sprinkled about to show there's power of relation there.

and that's what i said. set theory is helpful as a brick. category theory is helpful as an architect.