This is tragic.
Language is really important, to a degree that most mono-lingual people just do not fathom. I am mono-lingual, when I was younger I thought language was just a way to communicate. That language diversity is a bad thing, because it creates barriers between people groups. I thought that in a globally connected world not knowing the most popular language puts people at a disadvantage, so we ought to all learn the same language, and obviously that should be the one I grew up with.
That is a deeply colonial mindset. English, French, and Spanish are only as popular as they are because of Colonialism. The world is globally connected today because certain groups of people worked very hard to conquer, exploit, and repress everyone they could. This process continues today, in different forms. The unmitigated disaster that is the Climate Crisis has been a direct result of colonization and the economic system it created. Nearly every component of this situation, climate emergency, language extinction, globalized planet, is the result of horrible systems and acts. So the idea that people should try to fit into this world, that easier communication on the terms of the conquerers is good, is wrong. I was wrong, and you might be too.
The other part of this that's important is the value of language. I will focus on one aspect of that value. More than simple communication, the languages we know structure the ways we can think. The relationships between concepts in a language, as well as the concepts themselves, set the stage for the sorts of thoughts a speaker (or signer or writer) can have. Language diversity matters in part because diversity in language means diversity in thought.
There are whole sets of concepts you and I cannot fathom, because we lack the linguistic framework to explore them. This touches everything we experience, from emotions to gender to philosophy to law to the common experiences we have every day. Look around you, and I'm sure you can find something you lack the words for. The particular way that a tree's branches connect and sway, the vast variety of sounds that machines make, the particular feeling of knowing something you can never hope to fully convey. And I'm just an English speaker, think of all the possible ideas that these peoples who are losing their languages do have, and imagine the infinite possibility of what they could concieve. Such a tiny sliver of life thinking is, but even it's consideration overwhelms me. What endless beauty there is in the possibilities our lives contain, yet all of it is being systematically destroyed. There is a feeling I get when thinking about this, maybe you get it too, "tragic" feels inadequate for such a thing.