One of the driving forces of math achievement is an internal award (yes, friggin business speak).

The vanity, fame, self-improvement, it's very selfish as everyone does.

Now the fame coming from proving things like Riemann Hypothesis is taken away. Self-improvement? relying on AIs make you stupid. It will be lost. Vanity? Who else don't know how to use AIs? It cannot fill your void.

Now also the most important thing is the communication.

There will be less communications amongst mathematicians at least in person. On paper? maybe but mostly via AIs.

I don't think it's the communication that's lost, it's the motivation. People love to collaborate, but they don't always want to waste time doing it.

It's the same reason you see 'no AI' repo labels: only by forcing some standard on the community can the 'old way of collaborating' continue to exist.

There will for sure be new ways of collaborating, and walled off gardens like you suggest, where communication stops and everyone just shares some final product.

But, in some cases the product must be understood (or demonstrated) before value can be derived, and so collaboration will still exist.

Desire, and the 'shape' of collaboration has changed greatly though. Why collaboration has changed, is a completely separate issue related to economy and how each of us spends our time.

The fame from solving the Riemann Hypothesis has not been taken away. It's still open.