India is very diverse, yes.
I think that it's good for the people: the people of India are also very diverse; and if the diversity was somehow lessened, then someone would be discriminated against (see: the treatment of Hindus and Christians in Pakistan vs. that of Muslims and Christians in India).
Again, a comparison with Pakistan is on order: if you want to know if India would have progressed faster if the land and the people were not so diverse; I don't think so. I think that the diversity is actually what let India develop a bit faster than the less diverse Pakistan (remember, they were one country in 1946, so they were very similar, but today I think India is stronger economically.).