"Dear 13th-century Magical Oracle, It is possible to transmute lead into gold?" "Yes. This pile of giant incomprehensible spaghetti[0] is the irrefutable proof that it is possible."

What did the alchemist truly learn from this interaction? Is the answer in any way helpful for him? Will it lead to him making gold, and the implied endless riches it entails? Why should it bring him him to ask follow-up questions with useful answers like "The technology to do this doesn't exist yet and can't be developed within several lifetimes" and "It'll never be economically profitable to turn lead into gold", instead of blindly being fed piecemeal steps in the impossible task of one medieval guy building a LHC?

Writing true statements is absolutely trivial, anyone can do that. There's an endless amount of true statement which have absolutely no value to humanity whatsoever. Their proof is meaningless without something to give it context. "Substatement 1304 is true" has significantly less value than "here's something I call 'group theory', and it might also be helpful solving open issues in fields X, Y, and Z".

Mathematics is about widening our collective understanding. There will of course be some people out there who'll hear "The answer to life, the universe, and everything is forty-two", think "Neato!", and go on with their day without giving it any further thought - but I'd have a hard time calling them mathematicians.

That doesn't mean it is completely useless, of course. A "prove that no efficient algorithm exists to break this new encryption scheme" would be very helpful indeed. Until you realize it neglected to take quantum computing into account, of course.

[0]: https://home.cern/alice-detects-conversion-lead-gold-lhc/

AI in mathematics is forcing big questions