Endgame?. Lazaridis says Armenians , Greeks and Albanians descend from Yamna. Also Tocharians. And the Southern Arc paper is out. The link below.
The same for Tocharian speakers: they presumably lasted for >3000 years, long enough to record their languages, even briefly, in medieval times, before their languages went extinct. It's an accident of history that we have evidence for them at all.
And 99% of Indo-European speakers stem from Corded Ware ancestors. It is only three small groups: Greeks, Armenians, Albanians who go up to the Yamnaya not via Corded Ware intermediaries. Many others were wiped out linguistically, e.g. Tocharians and most Paleo-Balkan speakers
It's basically a series of unlikely events that make it possible for us to reconstruct the early history of Indo-Anatolian and Indo-European languages. And, presumably, other important languages were lost, but what survived is, I think, enough to recover the big picture.