If they think capitalism is markets and debt, which have existed basically forever

That is exactly what they think. That’s why they think we’re the fucking idiots. How could any human civilization exist without trade? The progression through modes of production is a completely alien concept to them. They don’t even conceive of it as a transition from feudalism to capitalism, or that this transformation is what gave birth to liberalism in the first place. They conceive of it entirely as a cultural / philosophical transition from monarchism to liberalism. And then technology got better at some point. And the economy got bigger. And all of these things just happened on their own, independently.

Human civilization just sat around for thousands of years with its dick in its hand until one day somebody thought, “what if we voted for shit?”