A great filter needs to apply to every civilisation imaginable, no exceptions, nerfing billions of species before they get to a higher Kardashev scale, not just something that "could happen" or the latest “Dunning-Kruger” mic-drop in every thread. In 1960s "the great filter is nuclear war", in 1890 "the great filter is heroin", in 1918 "the great filter is world war, we are destined to destroy ourselves", in 2015 "the great filter is climate change our emissions will end us like bacteria in a petri dish", in antiquity "the great filter is the punishment for crossing the will of the Gods".
It's got to be something you cannot get around even if you try really really hard and get very very lucky, because there are ~200,000,000,000 stars in the Milky Way and with those numbers there will be some species which lucks its way past almost any candidate, spreads out and in a mere 100k years is all over this galaxy leaving rocket trails and explosion signatures and radio signals and terraforming signs and megastructures.
Maybe when NASA, ESA, SpaceX, RosCOSMOS, CNSA, IRSA all collapse because of this effect… look how many countries have a space agency! https://en.wikipedia.org/wiki/List_of_government_space_agenc...
https://en.wikipedia.org/wiki/Great_Filter