Yes, but religion also have their own heritage. If India is only about Hinduism, people of other faith would not feel comfortable and being inclusive in the country of India. But I'm certain that is not the case so it's best for Indian government to emphasize on being more inclusive
Forget linguistic or regional diversities, just religion only. India is the birth place of Hinduism, Jainism, Buddhism, Sikhism among a few others and all of them still exist and thrive in India. India has one of the largest populations of Muslims in the World who have been living here for last thousand years.One of the biggest Islamist revivalist movements, Deobandi, is based in India. India has many states where Christians are in majority. All forms of Christianity, Catholic, Protestant, Orthodox are practiced in India. India has very last of the very few Zoroastrians remaining, probably they have ceased to exist in Iran itself.
India is a boiling pot for all kinds of people having different language, culture and faith. We celebrate accordingly too.
I am a Hindu and I celebrate Christmas, its a national holiday. My friend is a muslim and he celebrates Durgapuja with me.
So, let me assure you, India is not just about Hinduism only.
Its an old World and we have our own culture and heritage, which is again affected by language, region, and religion. Generalization of the same from a singular perspective will be a naive thing to do.