Yes, that's true of commodities generally. They are worth what people will pay for them; they do not produce cash flows. A pile of copper is not productive either.
The fair criticism, I suppose, is that the "compelling reasons" a person might pay for a pile of copper are much more numerous than for gold (or bitcoin).
But, OK: think of fine art for a moment... it is also an unproductive asset, the value of which depends wholly on what other people feel like paying, since there is no immediately profitable economic activity in which you can engage with a Monet (unlike the pile of copper). Are you therefore calling fine art a pyramid scheme? I think we are watering down the definition into meaninglessness.
