From an utilitarian viewpoint, sharing a single, global language is probably useful. but I feel that such a world would likely also suffer from less variety in culture and viewpoints.

Languages tend to accommodate the way of thinking prevalent in the cultures that speak it, and vice versa the language also shapes the speakers. To learn another language as a non-native speaker, especially one that is sufficiently different from your own, you must also learn a different way of looking at the world; something that I think is a useful experience for anyone.

Before reading the article, had you ever considered that there might exist a word describing exactly why cat videos are popular?

In my opinion, no-one should be satisfied with speaking only one language, so long as they have the means to learn another.