> A free market does not mean a market where a buyer has a choice of not buying something. It only means one where the market choices of agents are not constrained by coercive intervention of other agents.
That's not how I was taught this concept. I know, Wikipedia is a bad source, but I would like to point out how widespread my specific interpetation is amongst the economics textbooks I've read;
In a free market, individuals and firms taking part in these transactions have the liberty to enter, leave and participate in the market as they so choose. Prices and quantities are allowed to adjust according to economic conditions in order to reach equilibrium and properly allocate resources.
Note, enter and leave. This means both as a producer and a consumer, without this we cannot have efficient allocation.
> We need to buy food, but the market for food is still quite free, and consequently, very efficient.
The food market is a really good counter-argument to mine, but when I was first making my observations, I found that food is a very different market that was originally constrained in similar ways but isn't. First is that it's a "market" that's nearing globalized post-scarcity (this doesn't preclude localized scarcity). We produce enough food that we can feed the global population twice over https://ourworldindata.org/food-per-person (3k+ per capita for developed nations and 2k+ for underdeveloped ones).
Humans have reached this state due to government-sponsored research and sponsored application of revolutionary new technologies.
Second, our ability to process food has also led to a surplus in stored calories. We can feed ourselves even during catastrophes (though distribution will remain a challenge).
And third, historically (as I am not certain about this particular point, but it is consistent with my reading of history), prior to the green revolution, the food market was never this free - it has always been state managed to a varying degrees. From feudal lords and chieftains to the Roman grain dole, food has been a carefully managed resources until our time.
Due to its oversupply and heterogeneity, the food market has a very different structure and dynamics that are inherent to it. But, taking my argument at face value, I would argue that it is indeed possible to exit the food market - we can grow our own food! Even a small-ish farm with good practices can feed a family for a year or more using wild seeds, natural compost and herbicides alone.