I detest this view. Typical navel gazing, utility-uber-alles (at least for things that "I" am not interested in) programmer who is more concerned with some kind of compatibility (of course using IT examples) than anything else.

Even if we only strictly consider languages themselves, what if some people find pleasure in them? You can't say that what they enjoy doing is wrong with some argument for its utility - because the use and consumption of that language is a utility in itself. Neither can you confine them to these "museums" since they might want to use it outside of the halls of dusty books. Then, so much for "one and only one language".

Now, considering not just the language but culture. Languages are so incredibly context dependent and vague that I think they are deeply intertwined with culture. Outside of whatever you can laboriously define and enshrine in some book to stuff in a museum, there are incredible nuances that can be hard to appreciate if one is not involved with it, through things like social interaction and the written word. If you lose or discard the language of some culture, then you might also lose an appreciation for a lot of subtleties and ways of thinking. Words and expressions that might seemingly translate easily may have nuances that only an active speaker of the language can appreciate.

Thirdly. Consider if we with one magical button could make everyone in the world speak one language, say English. Now we are all on the same page! Then fast forward a few units of time - are we still speaking the same language? Probably, but we might have developed distinct dialects in different corners of the world. Why? Because every society and culture practising the language "evolved", namely added new expressions, words, phrases. Even pronunciation (accents). Why didn't the language simply evolve in the same way, worldwide? Of course because of the fact that the world is made up of a lot of different places and cultures. All of these cultures affect each other, but it's like a web of intermingling sharing. There is, largely, not a single, dominating culture, and so there is no central "authority" on how the language is going to evolve naturally. But you need a single "reference" point for this language to evolve in a uniform way, and avoid a lot of dialects! So if the goal is to have a single language, and a single dialect, your only bet is cultural imperialism. But culture is just a silly thing that just gets in the way, right? Better just stuff them in a museum and adopt a single, standardized culture. It's so efficient!

Given enough time, these dialects might turn into their own languages (let's say that languages are now distinguished by not being mutually intelligible with each other). Then you're back to the same problem, basically. Well, it's a lot better since all of these languages are closely related. And maybe these languages would never really become their own languages, since there is sufficient inter-cultural, global communication to avoid any significant divergence. But to eventually have no dialecs, no linguistic misunderstandings? Something's gotta give, namely everyone has to adopt the same culture and pallet of beliefs and values. But I guess that kind of robotic efficiency would be a Utopia for you.