I’ve always wondered why it gets so much attention as an early European concept when people had been speaking other languages for thousands of years, doing cave art dating back tens of thousands of years - it’s like history ignores it.
It kind of reminds me of how they treat “dark ages” when there was actually quite a lot going on intellectually.
With that said, most historical linguists would probably kill for more data on extinct pre-PIE languages.
Are you claiming that Basque has been spoken unchanged for 6000 years? Are you claiming that PIE speakers were speaking no language at all until they suddenly invented PIE from whole cloth while Basque speakers were speaking languages? ALL language in Europe were spoken only 6000 years ago, as far as I am aware, including Basque.
Plenty of historians pay attention to cave art but there is not much that can be concluded, whereas it is fascinating that we can reconstruct unattested languages from modern examples of language, include PIE as well as many other proto-languages across the world. For language isolates like Basque, there is simply less to work with, in terms of reconstructing, although there has been work done on "internal reconstruction" to try to extract what historical information can be inferred from variation in a modern language.