> The caste system prevent a huge part of the population to contribute to the demographic dividends

Over the years India has implemented several affirmative action programs (locally called "reservations") that ensures a more level playing field.

India has actually done reasonably well economically since 1995. Unless you can point to specific studies that correlate India's less-than-spectacular economic performance to the caste system directly, this is a fairly baseless statement. You only have to take a quick look at the last 10 year average GDP.