Every final (non-waste) output of a capitalist system is intended for human consumption. Compost, pet food, sheet metal, etc are all intended to satisfy human preferences. Price signals ensure that only things which humans value are economic to produce.
OK, that's optimising for efficiency, not for human values. If capitalism optimised for human values, we'd all be paid to house the homeless, free slaves, improve conditions in the global South, heal the sick, feed the hungry and so on.
That's not how values work - people go against their values all the time due to incentive structures. I want everybody in the world to be fed, but not at the cost of myself being tortured for a million years. Our goal as a species should be to align our incentives with our preferences so the behaviours that get rewarded are the ones that we want to see.
Every final (non-waste) output of a capitalist system is intended for human consumption. Compost, pet food, sheet metal, etc are all intended to satisfy human preferences. Price signals ensure that only things which humans value are economic to produce.