Well, let me amend this. An ancap economy is certainly possible. Whether it looks anything like (neo)keynsian macro markets is another story—but economies are always possible. But yes, in general, stable societies should be extremely aggressive at paring down the wealth of successful people, or they will be subsumed by them.

And let me re-emphasize, private markets are generally a terrible thing for most people who aren't already being starved by their state. This does not generally result in efficient processes in the short term, and we're discovering in the long term private markets don't encourage competitiveness either.

...but when we talk about private markets (i.e., public markets of mostly private things), we neglect the real private markets, aka "platforms", aka app stores and subscriptions. These aren't even pretending to provide the benefits of market-driven societies.