It would only be part of the answer but the most striking thing to me is that AI lacks the inherent sense of minimalism most humans have because creating code is so hard for them. It's so hard that a large part of our initial thinking will simply be to minimise the solution down to the least possible change from current state.
AI tools do have a little bit of this but I think it's heavily in conflict with more recent efforts to increase their persistence and the scope they can undertake and length they can work on something. All these have been optimised to hill climb coding benchmarks, but put against the benchmark of "are you sure you really need this at all? Couldn't we do it a simpler way? What if we just did it X way and then we only need to change 10 lines of code" - they are not even being tested against this metric.