I think you're missing the point, they point to our extinction by our own hands. If millions of alien species have tried to survive through an era of technological advancement, and all of them have failed, that suggests that we don't have much chance of surviving either. We'll probably fall into the same talks that all of them have.

If on the other hand, we saw lots of alien civilizations existing somewhere out there, or even some civilizations, that would suggest that as long as we don't totally screw things up, we at least have a chance. Survival is at least possible.

And while it may look like we're screwing it up, to be honest, things aren't so bad. There have been a lot of mass extinctions on this planet, but there's still life. The planet has both been much cooler and much hotter at various times in the past, there's still life. There's really no guarantee that we're going to kill ourselves, things could turn out fine. But on the other hand, what we're seeing when we look around the galaxy is not super encouraging...