Dude....
I am using my definition of multi-ethnic country and not anyone else's.
My definition is any country where the most dominant ethnicity is less than 50%.
All those countries you mentioned has the dominant ethnicity at more than 50%.
Both India and Pakistan are doing very badly and multi-ethnicity is mainly to blame. Luckily Pakistan is much better off as the dominant Punjabis are nearly 50% of the total population.
BD has surpassed Pakistan in nominal per capita and it is growing it's per capita at 7% a year compared to just over 1% for Pakistan. Please try to understand why BD finds it so easy to grow and India and Pakistan struggle.