No, it's an honest thing to say. If you're not able to read a graduate-level textbook and teach yourself category theory then you don't have the mathematical maturity to understand category theory. You need to start smaller: ideally abstract algebra and point-set topology, or set theory and mathematical logic if you just want the CS applications. Likewise with Lean. Of course there is a place for a good human instructor. But mathematical maturity must be developed the hard way.

Even if you are correct, which you aren't, a good tutor almost ALWAYS helps people learn faster. This is just a really odd thing to argue.