That's communist thinking. In communism, we only produce as many goods as people actually need, and nobody goes without, so demand is always fixed. But in capitalism, there's always more poor people going without you can sell to, and even if demand is fully met, you can keep producing goods to sell to stores who'll throw them in the garbage, and you still make money.

A lot of very bad decisions have been made by people who expect a capitalist economy to work like a communist economy. This is a completely reasonable mistake to make, because human beings are naturally communist. But it's still important to remember that we don't live in an economy that matches our natural intuitions. We live in capitalism.