Why don't you consider mutual intelligibility across nations to be good? I love the diversity of the many languages we have, but that's not really a useful aspect of the World - greater cooperation seems to me to be a noble target for the human race and commonality of language seems to aid that. People can share their unique culture with me because they speak a language (native, domestic, or otherwise learnt) that I can understand.
Mutual intelligibility for the sake of information exchange is good, but we can have both. Most Europeans already have both. In the EU (the organization) it's Euro English.
The person above you has not said that mutual intelligibility is bad.
You want people to share their culture with you, yet you are fine with them throwing away something which acts as one of the backbones of their cultural history for the sake of an imagined increase in cooperation.
And also, why does everything have to be useful? The useless things in life are often the best. Like ice cream, poetry, wasting an afternoon away, or hacking. In fact that's why I work, to enjoy the useless things in life.
Not everything has to be useful: you used the same technique there you implicitly criticised me using ;o)
Communication, is for communication. Yes, it's good to have localised codes, domain languages, private communications; quirky ways to make crypto-poetry, or to create artistic expressions.
But we, IMO, should be very wary of placing those above or ability to communicate effectively with as many people as we're able.
In Welsh counties of the UK school children are forced to learn Cymraeg, a language that doesn't help them access any other cultures, not communicate with any other people they can't already (except literally one or two pre-schoolers).
Cymraeg is very interesting and holds together part of the story of UK, my home country, but for communication it's a bad choice.
I've no problem with people choosing to learn languages for purposes other than communication; but forcing schoolchildren to learn a second language that's near useless [compared to global modern languages] as a communication tool, that's awful.
Yes to historic languages; no to forcibly separating peoples through choosing purposeful separation via language.
