In a way, that’s the situation today. You can pay an experienced developer $$$$ to do it right, or you can outsource it and pay $$ but pay extra for more layers of review, have lots of unfixed bugs and more tech debt.
You are proposing that instead we pay the frontier model to clean it up. If it can, I expect it to cost somewhere in the neighborhood of an experienced dev because that’s the alternative. That’s the way the frontier AI companies will extracting the value of the work from you.
But there's two ways this could be true: Frontier models costs rise, or (more likely) experience dev costs fall
That's only true if a single company owns the frontier, otherwise the alternative is "a rival frontier model" and the cost will be the marginal price of the compute + amortized training costs.
You're car will have spun off the road and you'll find it harder and harder to control it and keep it on the road because you have less and less visibility into the vehicle, nor will you be able to clearly see out your windscreen to use the car and road metaphor. You'll be driving blind eventually, unless your working on some simple closed toy problems and/or other small systems.
Building large systems means understanding the system. Without understanding the system, you lose control of it.
The LLM can probably help you understand the system to gain/regain some control of it again, but now you're becoming a system specialist rather than someone who's repeating, "fix it" and "make it good" or whatever.
Self-trained people (like me) are particularly susceptible to it and we're heavily represented in the software world. A lot of us either recognise that (or are coached) and invest the time learning the benefits, and limitations of, software architecture. And, importantly, keep reflecting, learning and updating our practise.
I keep going back to the YOLO mode every other year and try out new languages to see if we still need the structure and abstractions. Then VMs came along and all I can say is they're both even more important and now we have an army of virtual "ADHD idiot juniors developers" at our finger tips it's even easier to tell the good and bad abstractions from each other.