I disagree, e.g, europe, not pure capitalism, not pure communism, not pure socialism, but somewhere in between (depending no country). Overall these countries are not less successful than US (which is also not pure capitalism), and most of it citizen prefer living in europe and would not consider moving to the US. More socialised forms of healthcare, education and unemployement support are main reasons.

Every country in the world and every civilization in the history of mankind is an example of "what else?". The US isn't run on pure capitalism, and it never has.

Some countries do better than others, in various metrics. That's the "what else" you can look at and emulate.