From the Encyclopaedia Britannica [0]: __These conspicuous declines in diversity are referred to as mass extinctions__
> It also doesn't mean all species who didn't thrive would be lost - many would be affected but not existentially so.
But this is not a fact, it is a conjecture. On the other hand, we do have declining numbers of a big number of species. Unless the tendency reverts, constant long-term declining numbers will be an existential threat.
> I'm reminded of George Carlin's joke about the planet being fine long-term, we're the ones who will be screwed.
That's true, for sure. But asides from "the planet" and "we", there are also all the others.