This has the same issue I have with any theory where the great filter is a technology that evolves roughly contemporaneously with spaceflight (like atomic weapons): It’s just not probable that _every_ civilisation would destroy themselves before being multi planetary. By virtue of the events being so close, some civilisations would escape destruction if only through dumb luck.
Personally I think the lack of visible galactic civilisations is more plausibly explained by a combination of life being rare (and probably brought to Earth via panspermia after billions of years of evolution elsewhere) and both multicellular and sentient life also being rare.
Personally I think the lack of visible galactic civilisations is more plausibly explained by a combination of life being rare (and probably brought to Earth via panspermia after billions of years of evolution elsewhere) and both multicellular and sentient life also being rare.