Language is culture, and if the sapir-whorf hypothesis holds, different languages are literally different methods of thinking.
there are also other potential benefits, e.g. "the" in english gives little information about what noun may follow. "die/das/der" in general cut the probability space to a third.
When speakers of a dying language learn a dominant one they don't lose their way of thinking, rather they adapt the dominant language to their needs. In this way the dominant language evolves. It's why there are ~180k english words but only 1200 Sindarian words.
While I agree that cultural loss is tragic, consider that it is inevitable. Homo Sapiens have existed for ~200,000 years. We only have SOME traces of SOME cultures for say 10k of those years. So from that lens, the vast majority of human culture has already been lost.
From a practical point of view it is probably good to have an international lingua franca, most likely a variation of English not only due to its current popularity but because it has accommodated a lot of simplifications [1,2] to make itself easier to learn. But for local cultures it would be an awful lot of work to translate centuries of tradition and literature into a global language, or a lot to lose by forgetting it. There is also a natural human tendency to modify and evolve the language that we use, while an international language has to be more stable or changes regulated lest it fragment as Latin did 1500 years ago.
Kids cannot use foreign language tools to their full abilities. However, if ChatGPT is good for english only, it might stimulate some competition for providing similar service in the local language. I won't mind it, tbh.
