There are some pockets where this is not true, but they are exceptions.
And those comments aren't defending it.
Upward mobility is available in India, too. But remember that to have "upward mobility", there needs to be place at the top. For a country which has been under hundreds of years of regressive colonial rulers, there is not much place at the top.
Global wealth is much more in the US than in India right now, so it is not wise to compare rags-to-riches of the US with those of India.
India's government jobs, elite engineering and medical seats have a legal 50%+ quota for "lower" castes people. Did you know that? So, I am saying, 50%+ students graduating ALL elite engineering and law and medical and nursing schools, etc. are from these "lower" castes. Did you know that?