If you paid doctors less, there's no reward for spending your entire 20's and early 30s in training, already earning almost nothing. Nobody, especially nobody talented, will do it.
It's already probably not worth it from a purely financial perspective, when you consider the options would-be doctors have (they are among the highest performing students already -- they could easily be lawyers, professors, engineers, etc).
The real growth in medical costs are from administrative overhead and the vast new amounts of paperwork that doctors have to spend their time shuffling.
If doctors spent 80% of their time in patient interaction or actual diagnosis, there would not be a perceived doctor shortage. Instead, it's 70% paperwork and filling out forms to check the right regulatory boxes. Increasing productivity by culling the paperwork and regulatory bloat will be vastly more productive than pumping out more low-quality doctors.