Plus this goes against the common narrative that these craft display propulsion capabilities that appear to defy physics, which (if we're assuming aliens) implies anti-gravity at a minimum. No one is claiming to encounter UAPs or UFOs with wings and conventional rockets. Again, that's something we only kind of know how to do on a napkin, and even then only if we fudge the numbers.
At the very least, I would want to assume any civilization capable of interstellar travel to be at least 1000 years ahead of us, technologically. Even with generation ships and no space magic. It's just a big stupid round number but I intend it to mean generally as far ahead of us now, in terms of scientific knowledge and technological progress, and assuming a few paradigm shifts ahead, as we are ahead of the Middle Ages.
My guess is that we'll be able to develop human-level artificial intelligence a lot sooner than 1000 years from now.
At which point it would be a lot easier to send AI probes to explore the galaxy and/or make first contact with another civilization than to build a generation ship.
The odds of bumping into an alien civ that is anywhere near technological parity with us are vanishingly small. Given that the universe has been capable of hosting habitable planets for ~10 billion years, the median age of alien civilizations could easily be billions of years old. Meanwhile our civilization is a paltry .00001 billion years old.
It could be that the only ones we'd actually bump into are those who built and launched generation ships not too long after they became capable of it, which would be when they are not too far ahead of where we are now.
Right now we just don't know enough to say what it is like out there. We do know that we sure haven't been able to detect any signs of alien civilizations. But we don't know if that is because very few civilizations start, or they start but something kills them before they start doing things we could detect, or they are only at a stage where they are doing such things for a relatively short time and then they switch to technology that we can't detect.
The absence of evidence isn't evidence of absence. We've only been "looking" for life for ~50 years!
> It could be that almost all civilizations suffer an extinction event before they get technologically advanced enough to prevent it or survive it.
It seems to me that we've got three possible scenarios here:
Scenario A: There is NOT a Great Filter. In this scenario, we have a large number of civs with a high median age. Scenario B: There IS a Great Filter. It catches between 0-99.99% of civs. In this scenario, we still have a large number of civs with a high median age. Scenario C: There IS a Great Filter. It catches 100% of civs. In this scenario, we have a small number of civs with a lower median age (some ${Civ Age at which Filter Occurs} / 2)
It's hard for me to imagine that we're living in Scenario C. For a Great Filter to catch 100% of civs, it would have to be baked into the laws of physics!
Even then, the Great Filter would have to occur VERY early in technological development for the odds of technological parity to be good. And, of course, an early-acting Great Filter means fewer extant civilizations at any point in time, lowering the odds of an encounter occurring in the first place.
It's not obvious that aliens who reach Earth must be much more technologically advanced than we are. They could have come here in a generation ship, which probably only requires builders who are a little ahead of us, and that only in fields like bioengineering.
For most of what they'd need for a generation ship our current level of technology is fine. In particular there is no reason they would have to be better than us at aircraft or weapons technology, so whatever vehicles they bring along to use when they want to enter a planet's atmosphere might be no better than what our current air forces have.