Well, I just did. What's wrong with it?
I mean, look: the thread has a caveat in it, right there in the title. "(sort of)" And the sort of is a nod to the actual operation of the market today, as opposed to 75 years ago or in theory. I would say that private health insurers, all else being equal, help control costs and improve patient care. There's nobody else who can represent patients' interests collectively. But all else is not equal, right? I pointed to the way employers are involved in paying for care, and how that has made our system greatly suboptimal.
Some research I did a long time ago with my gf at the time (she has since made a career as a health policy expert) also showed that employer-based health insurance disincentivized preventive care. Basically, the idea is that insurance companies would be happy to invest and even encourage preventive care for their insureds. . . . except they have no idea whether their insureds are still going to be insured by them in their healthier futures. Because employers' shop around for insurance, and people are generally not free to continue with their existing plan if the employers change insurers, insurers can't reasonably invest in preventive care. There will be an insurer who doesn't pay for preventive care, and then swoops in to grab patients from other insurers who did invest in preventive care, and this free riding problem discourages preventive care.
So I'm very far from being an apologist for our current system, which is not the way anyone would design it from the ground up in today's world. It is important, though, to put responsibility where it belongs. Insurance companies get way too much of the blame and hate for what people hate about our health system. They are a necessary part of that system and are captive to it just like providers and patients. They aren't necessarily evil. In our system, they perform a valuable function and a cost-saving one (compared to the baseline alternative, at least). One reason people hate them is that they are the bearers of bad news. And the system also helps make them monstrous.
The nasty reality of health care in America is that we have more demand for health care than supply. That's true for a number of reasons (including the supplier inducement I described earlier, but not only that), but the point is that it has to be rationed. We currently ration by ability to pay (except in Medicare, and even then there's some of it), which is a lousy way to ration. But rationing is never fun. People get denied care in other countries as well, and sometimes they come to the US to get it. And if they don't -- well, they become unhappy with the health care system because rationing is no fun.