> But do I “understand” the proof of Fermat’s Last Theorem, given that earlier this year I gave 22 hours worth of lectures on the topic?

Even if no one human can understand the entirety of a complex proof, surely we can piece together multiple experts' separate understandings, so the community as a whole 'understands' the proof?

Is there value in us 'understanding' a proof? Even if no single human can understand a complex proof soup-to-nuts, and we have to piece together several experts' understandings?

If the answer is Not really, then the value of a proof is its utility, its utility in making new products/services, and its utility in making new proofs. If in the case of abstract math, all the utility is of the latter kind (making new proofs), then we have a pyramid scheme here.