Though there's been some research recently showing that younger doctors are better, because they're aware of the latest research. I wonder if that's going to lead to some ageism in medicine because of that.
This is a myth perpetuated by medical schools. There is no regulatory limit to the number of residency slots hospital's can create. There is a limit to the number Medicare will pay for, and teaching hospitals generally refuse to create slots that are not paid for by Medicare.