I keep asking myself the same questions, and the conclusion I keep coming to is the clean modeled structure we want to see is for humans to maintain and extend, but the AI doesn't need this.
There's definitely an efficiency angle here where it's faster for AI to go from a clean modeled solution to the desired solution because it's likely been trained on cleaner code. Is this really going to matter though?
The best argument I can come up with is the clean modeled solution is better for existing development tools because it's less likely to get confused by the patch work of vibes throughout the code; but this feels like it ultimately becomes an efficiency concern as well.
This just might be the new reality, and we need to stop looking behind the curtain and accept what the wizard presents us.