I'm no fan of Medicare Advantage (or indeed of Medicare in general), but it is not a "free market" program. It has the same problem all socialized health care programs have: the people who are actually getting the care, patients, have no idea what it costs, so they can't judge whether the care they are getting is worth the cost. A free market program would be one in which the patients paid the costs directly and could shop around for the best deal, just like in the rest of the free market. If you want to help people who might not have the money to pay those costs directly, the obvious thing to do would be to subsidize them, the way we subsidize food purchases now for the poor with food stamps. Food stamps just give people a monthly sum they can spend on food; they don't go and negotiate prices with all the grocery stores and then argue after the fact about whether a particular food purchase was covered.

It is true that in some situations, like emergencies or accidents, patients can't shop around. That kind of situation is indeed what insurance is for. But programs like Medicare, and indeed socialized health care in general, go way beyond insurance. Insurance is for high cost unforeseen events. Most health care is not high cost unforeseen events; it's foreseen events like physicals, shots, checkups and prescriptions for chronic conditions, etc., or low cost unforeseen events like getting an infection and needing treatment. If all of those things were provided in a free market, health care providers would be much more efficient, and it would be much easier to negotiate reasonable terms for insurance for the truly high cost unforeseen events that insurance is for. Medicare Advantage (and Medicare and socialized health care in general) is of course nothing at all like that.