Diversity is not necessarily a barrier to communication. (In fact, the idea that diversity is a problem and a barrier to communication is itself a bigger problem IMO.) In India most people are multilingual, and there's usually a link-language. For instance, in the region mentioned in the comment you're replying to, probably a majority would speak Gujarati too as a second language, and a significant number of them Hindi, and many English as well. There's going to be a fair bit of interchange and translation going on too. (For example, even in the Anglosphere one is not completely blind to French or Italian or German language or culture, say, and is aware of at least a few of their peaks: enough to recognize they have something of value too.)
The existence of diversity is generally a sign of freedom and self-sufficiency: that the people in question were/are free to retain and develop/enrich their own culture, and yet function successfully (enough) in interaction with the broader society, without too much pressure to give up their ways. (See: “melting pot” and “salad bowl”.) Monocultures, monolingualism, monotheism, etc., do have certain advantages too of course, but I hope some can see why diversity is valuable too.
The existence of diversity is generally a sign of freedom and self-sufficiency: that the people in question were/are free to retain and develop/enrich their own culture, and yet function successfully (enough) in interaction with the broader society, without too much pressure to give up their ways. (See: “melting pot” and “salad bowl”.) Monocultures, monolingualism, monotheism, etc., do have certain advantages too of course, but I hope some can see why diversity is valuable too.