Anyone else feel like mathematics is sort of the endgame? I.e., once ML can do it better than humans, that’s basically it?
I doubt it. Math has the property that you have a way to 100% verify that what you're doing is correct with little cost (as it is done with Lean). Most problems don't have anything close to that.
Math doesn't have a property that you can verify everything you're doing is correct with little cost. Humans simply tend to prefer theorems and proofs that are simpler.
You can, in principle, formalize any correct mathematical proof and verify its validity procedurally with a "simple" algorithm, that actually exists (See Coq, Lean...). Coming up with the proof is much harder, and deciding what to attempt to prove even harder, though.