I guess whether this is a big problem depends on what you value. From some perspectives, knowledge and skills are not ends unto themselves, but only have utility in a specific context. For example, I care not that the skill of carving elephant ivory is basically a lost art at this point. Diversity? I can't say that the presence of nomads in the desert was really moving the needle on that very much in my daily life. A link to our past? Perhaps, but, as GP pointed out, only in the sense of a living museum exhibit. It is not like many people actually go to encounter this link personally, and in any case, even if they did, these are people.
I admit a certain amount of wistful nostalgia, but I personally don't consider nostalgia to be the same thing as sadness. Nostalgia is most often a delusion, not a genuine recollection of the good old days.
You're taking a very utilitarian view of these things. Nothing wrong with that. But many people enjoy knowing that there are still those who stick by their old ways without there being any tangible benefit to themselves or the rest of society.
I admit a certain amount of wistful nostalgia, but I personally don't consider nostalgia to be the same thing as sadness. Nostalgia is most often a delusion, not a genuine recollection of the good old days.