The golden age of languages is when there is only one language left, and everyone can understand everyone without cunning translators and hallucinating llms.
Unfortunately, even if we had a single language, I doubt we’d be free of misunderstandings. Jargon, double entendres, shibboleths and other barriers to understanding all still exist even when everyone is nominally speaking the same language
Knowing multiple languages, in particular less related or unrelated ones, is mentally enriching. If you only know a single language, you don’t know what you are missing in terms of diversity of thought and expression. Languages aren’t fungible. Translation is lossy, often considerably so.
Live translators exist! It has become much better than even a couple years ago
Isn't that a collapse in cognitive diversity?
Not to be "gotcha", but out of true curiosity: may I ask if you speak multiple languages fluently?
Different languages afford different ways of thinking and speaking? Just talk to a translator in works of literature or poetry. Some languages are more verb-y or noun-y, and so are more about getting between things than being something. Or have more or less ambiguity due to tonal systems.
And while ambiguity can create miscommunication when misused, it also allows for different minds to hear one thing, but interpret it in ways more personal to them. When used pro-socially (and not manipulatively), this can afford cooperation that might not otherwise be possible. Saying things while leaving some things unsaid, that has utility if our collective project is certain forms of synchrony -- we can sync on some things while the ambiguity allows asynchrony to remain unresolved in less important dimensions, etc
Imho monoculture is toward death, not toward something golden.