How so though? This sounds like a statement that's meant to be flashy but doesn't actually hold up. Pyramid schemes are characterized by a) an eventual lack of ability to recruit more people, b) recruitment rather than a product or a service being the driver, and c) a person at the bottom left with nothing, including recourse. Capitalism, even completely free capitalism, doesn't work like that unless you specifically rig it to do so. That's called "corruption".
an eventual lack of ability to recruit more people
Global population growth is slowing and predicted to halt within the next few decades.
The modern economy has always relied on an environment of growth, which will now end. In some ways this resembles a pyramid scheme; in the past anyone making investments in the economy could count on a larger new generation of people coming into the market needing to exchange their labor for those hoarded resources. Since this is no longer going to be the case, new entrants to the market are going to be getting a lot less for their effort than they may have expected based on past trends.
Like half the population of the world are poor, every industry is using behind the doors sweatshops. Essentially slavery. While not a perfect synonym, I think it makes sense