I've been reading about healthcare systems off and on, sometimes fairly seriously, for over 15 years, and my conclusion about the entire US system is that "the problem" is "literally everyone involved".
It's why various schemes that target one thing (say, excessively-expensive doctor liability insurance, which gets talked up as some super-big deal and a huge part of the problem in certain circles) are typically expected, on sober analysis, to have only a tiny effect on prices—everyone is taking too much money, at every level, so at most steps the % increase over what's reasonable isn't huge, but by the time you filter through a few layers of that with everyone piling atop the other layers, sure enough, it's a solid 30%-40% more expensive than it has any reason to be. But there's no one, or two, or even three things you can point at and say "if we fix this, we fix almost the entire problem". Every part of it needs a shake-up. It's like 20 different, though interrelated, problems, contributing to the bad result we see. Addressing most or all of the problem will take tens of measures, or else one big, sweeping, fundamental overhaul (M4A or what have you)