This requires a language that a human can give the specs in. A language that is both precise and unambiguous and understandable by humans. A... programming language?
And it requires AI to understand the effects of changes it makes. On many levels. "If I move this module behind an abstraction, will it make it easier to maintain? Does it touch performance? Would it open security issues?" Generative AI isn't good at reasoning in that way. Maybe other AI, but it seems hardly anyone is pouring substantial funding into areas other than "a bigger and smarter generator than the competition" currently.
From what I've seen, Grok 3 would be quite capable of inferring the effect of any change, at least at a high level. Have you used any of the recent models?
Current AI cannot, of course, but the trajectory seems to be that it will be able to do such things better & faster than any human can.