> India is/was a socialist state and I would expect social services to be spread more evenly than non-socialist countries. I also believe mobility is easier in developing nations and was better to some extent right after the Industrial Revolution and workers rights movements.
Saying "India is a socialist state" is, well, technically correct (it's in the Constitution) but a pretty misleading way to characterize the sort of social mobility in India that GP was talking about.
India is home to the longest-running continuously-serving democratically elected Communist government in the entire world. It's also home to what could be considered borderline anarcho-capitalist metropolises that are larger than many European countries.
As it turns out, the sort of mobility that GP is talking about is very rare in the states led by Communist and socialist parties, which have generally struggled economically[0]. It's most prevalent in the states (and cities) where the leftist governments never took hold, or where they were elected, but carried out very little of their vision in practice.
In any case, the scale of mobility and economic growth experienced in the economic hotspots of India (Delhi, Mumbai, Bangalore) has been made possible by the end of imperial colonialism, and the concurrent rise of a global economy. No developed country like the US will ever be able to experience that same level of rapid growth.
[0] There is one exception, though in that state, 33% of the state's GDP comes from foreign remittances (mostly from expatriates living in the Gulf), which is incredibly high, and higher than any other state. There is definitely an object-lesson in mobility to be learned there, but it's not the sort of mobility GP was referring to.