The premise feels mildly good to me, but I'm pretty sure some of that is positive affect bleeding over from my thoughts on alien life, survivability of sapience in the face of planet-killer events, et cetera. I'm likewise fairly sure it's not due to the bare fact of knowing about a population that I didn't know about before.

I don't get the same positive associations when I think about similar scenarios closer to home, i.e. "happy self-sustaining population of ten million mole people discovered in the implausibly vast sewers of Manhattan".