Most of a software project's lifetime will be spent as a maintenance challenge. i.e. How do we add the 237th feature without adding to the performance problems that already exist. Hence, the desire to rewrite the codebase to incorporate the abstractions of all 236 features.

I don't see AI helping with this. From my experience, it seems like the opposite. It can help you write the code after you've deconstructed the problem yourself and know how to keep it in check.