Attempt at the briefest content-full Less Wrong post:
Once AI is developed, it could "easily" colonise the universe. So the Great Filter (preventing the emergence of star-spanning civilizations) must strike before AI could be developed. If AI is easy, we could conceivably have built it already, or we could be on the cusp of building it. So the Great Filter must predate us, unless AI is hard.
I'd like to repeat the comment I had made at "outside in" for the same topic, the great filter.
I think our knowledge of all levels – physics, chemistry, biology, praxeology, sociology is nowhere near the level where we should be worrying too much about the fermi paradox.
Our physics has openly acknowledged broad gaps in our knowledge by postulating dark matter, dark energy, and a bunch of stuff that is filler for – "I don’t know". We don't have physics theories that explain the smallest to the largest.
Coming to chemistry and biology, we’ve still not demonstrated abiogenesis. We have not created any new base of life other than the twisty strands mother nature already prepared and gave us everywhere. We don't know the causes of our mutations to predict them to any extent. We simply don’t know enough to fill in these gaps.
Coming to basic sustenance, we don’t know what are the minimum requirements for a self-contained multi generational habitat. The biosphere experiments were not complete in any manner.
We don’t know the code for intelligence. We don’t know the code for preventing our own bodily degradation.
We don’t know how to balance new knowledge acquisition and sustainability run a society. Our best centres of knowledge acquisition are IQ shredders (a term meant to highlight the fact that the most successful cities attract the highest IQ people and reduce their fertility compared to if they had remained back in small towns/rural areas) and not sustainable environmentally either. Patriarchy and castes work great in in static societies. We don’t know their equivalent in a growing knowledge society.
There are still many known ways in which we can screw up. Lets get all these basics right, repeatedly right and then wonder with our new found knowledge, according to these calculations, there is a X% chance that we should have been contacted. Why are we apparently alone in the universe?
If you aren't sure about something, you can't just throw up your hands, say "well, we can't be sure", and then behave as if the answer you like best is true.
We have math for calculating these things, based on the probability different options are true.
For example, we don't know for sure how abiogenesis works, as you correctly note. Thus, we can't be sure how rare it ought to be on Earthlike planets - it might require a truly staggering coincidence, and we would never know for anthropic reasons.
But, in fact, we can reason about this uncertainty - ... (read more)