I've not had Medicare, but know it is fraught with issues. So is the VA. I've also been under American health care through a job, been uninsured, and now am covered under Norway's health care system.
And I wouldn't trade my current system. I'd rather have medicare than nothing, and know that the issues it has can be fixed. Just because something has problems doesn't mean that it isn't better than nothing and doesn't mean that it isn't a good starting point.
It might not be so bad being a doctor if we fixed some supply issues: For example, making sure doctors (and everyone else) doesn't have tons of student debt. We can do things about how expensive malpractice insurance is: My dentist here in Norway would like to live in the US, but won't because of the malpractice suits. We can do things to simplify the office work, such as standardising payment scales and coding. We can make good use of nurse practitioners, especially for children who generally have run-of-the-mill infections THese things make it cheaper to be a doctor and cheaper to run an office.
You'd think we might need to fire a lot of people... but not really. Single payer health care means we can do things differently because our resources are pooled. Norway, at least where I live, will send a home nurse to your house for free up to 6 times a day. Even if you are in a cabin in the mountains or living on a little island. This is all because overall, this is cheaper than a nursing home... which costs 80% of your retirement, no matter how much you make.
There is also a private system, which mostly gives bells and whistles. You might get into a non-urgent MRI sooner and so on.