In my experience a big part of the problem is specialists. I remember many years ago people were saying that we shouldn't go to a Canadian style single-payer system because Canadians had rationed care and they had to wait six months for a hip replacement.
Well, guess what? I now also have rationed care. I have to wait six months just for a colonoscopy, plus I pay twice as much for the privilege!
Part of the specialist problem is they make so much they realize they can work for ten years and retire, instead of working the 20-30 years that used to be common.
Without NPs and PAs, I'm sure there would be a shortage of healthcare providers.