Chetty’s work lumps together a lot of different people with very different circumstances. An Asian American born in the bottom 20% has a 25% chance of ending up in the top 20%: https://www.nytimes.com/interactive/2018/03/27/upshot/make-y.... Hispanic men born in lowest 20% have a 15% chance of ending up in the top 20%. That’s a high level of mobility. But black men raised in the bottom 20%, the chances of rising to the top are just 7%.

If you compare the US to for example Denmark, you can see that the lack of opportunity is concentrated in the bottom 20%. That is to say, income mobility is similar between the countries for people in the lower middle class, but not at the very bottom: https://thesocietypages.org/socimages/2012/01/05/economic-mo...

The various data taken together strongly suggests something else is at work rather than the economic system itself. Poor Asians, poor Hispanics, and poor blacks face the same economic system. For them to have vastly different outcomes in terms of economic mobility, the explanation is likely to be something apart from the economic system. What is billed as a matter of economic mobility may well turn out to be more of a story about the criminal justice system, systemic racism, the lasting effects of segregation, etc.