All good questions! We might be the only recognizably technological civilization out there, any other “life” might occupy something we cannot even tell is life.
I guess my point is that, provided we are not the only ones like us to begin with, concluding that we are still the unique ones that passed the Great Filter makes us pretty unique, and the question becomes “why?”. If AI x-risk is the great filter, then we would see the artifacts of it out there, unless the AGI magically stops growing somewhere between the current level and the observationally visible one.
Well, we do know that interstellar travel is possible, just currently very hard. It’s a technological issue, not a physical one. I can certainly imagine slow travel, a few thousands km/s, being possible with nuclear rocket propulsion or other tech. Getting a spaceship-size object traveling at an appreciable fraction of the speed of light is a different story, anything like that would create observational artifacts visible from far away, so those probably aren’t anywhere in the observed past light cone. But I am not sure how this is related to the evaluation of the odds of AIpocalypse.