If you're only willing to pay nothing your purchase will be worth nothing.
In particular if you want free medicine you will get not-medicine. You become the merchandise, not the customer. The social function of "universal" medicine is dysfunction; to make doctors rich. It's very effective at its genuine purpose.
Again, Communism is a bad idea, even on paper.
Although, ironically, the ROI on getting rich through doctoring is negative. Gnon punishes doctors for endorsing Communism by making them work in brutal, barbaric Communist conditions. They really do get rich, though. There's no demand for having a soul, and lots of demand for big houses and fancy cars.