I don’t think Bostrom’s technology urn doomsday argument makes sense as a great filter.  A civilization that was one connected organism wouldn’t destroy itself. So the galaxy should be filled with them given that it takes 20m years to populate it using nuclear propulsion.

what's your preferred theory to explain the great filter paradox then? 

if you want give two, one plausible with science we know, one plausible assume science we don't know. for example they just ascend to an higher dimension or whatever

dev, armchair economist & crypto tea leaves reader - 

/futarchy /network-states

Occams razor. Life is rare, it took 4b years old to get going on earth out of 14b years in the universe. We are most likely the first within our visible light cone.