Earlier quoted context omitted.
Language is pretty foundational to culture. When you lose a language you lose more than a way of speaking, but also the subtleties and emotions behind the "shape" of certain words, not to mention those words that reflect something so unique to that culture that you can't really translate them. The death of a language is the death of a world. Saying there should be fewer spoken languages is frankly a very unempathetic…
Saying there should be more different languages shows an ignorance to both history and psychology. Having less major cultures has the same effect on potential conflict
You're basically asking people to sacrifice their lives to a less useful language, a mere social utility, so you can maintain a sort of "cultural linguistic zoo" ... and yes you are by this analogy relegating them to the role of animals in a theme park.
Think of what that entails: "No, you can't be taught in the language that will get you into university and get you the best jobs. You must dedicate a significant portion portion of your life to something we already know is a dead end for you personally, because we have decided that it is more important that a legacy tool be kept alive than that you prosper as a person."