We’re not talking about “capitalist systems” though, we’re talking about “the market”.

“The market” existed long before capitalism. It’s an essential feature of human trade. Buyers offer goods for sale, sellers choose what they want to buy. People voting with their dollars, or with their cowrie shells provides a signal for what’s in demand and what producers should make more of.

Every system that has tried to get rid of the market has failed, and the market always pops up anyway, often in the shape of a black market.