Earth life may already be post-filter.

Also, I would bet on there being lots of little filters rather than one great one. Stack a dozen or so independent filters that only 1% of upstart life can develop through, and you can easily explain the apparent absence of life capable of broadcasting their existence, making life as developed as humanity extremely rare.

Maybe only 1% of stellar systems are arranged appropriately with a Jovian planet to sweep the inner system clean of killer comets and meteors. Maybe the conditions for unicellular life only occur on 1% of nominally terrestrial worlds. Maybe only 1% of unicellular life develops in a way that has a hereditary mechanism that is susceptible to random mutation, so evolution has something to work with. Maybe the jump from unicellular to multicellular is extremely unlikely to occur; it did take billions of years on Earth after all, its clearly not something that you can count on happening a week later. And maybe the chance that multicellular life develops in a direction that will eventually develop animals capable of making advanced tools is extremely rare too. Real life evolution isn't like a game of Spore, it's not a computer game with a defined goal that some force is working towards. Evolution likes robust reproducers like bugs a lot more than it likes clever monkeys. Maybe when intelligent animals do happen to evolve, they, like dolphins or octopus or corvids, almost always lack the physical characteristics necessary to put their brains towards the problem of the scientific method and industrialization. Maybe when such species even do exist, they usually socially stagnate in preindustrial times, as humanity did for a long time, and get stuck there because their culture values social stability more than innovation. Maybe only 1% manage to not nuke themselves out of existence within a few years of inventing nukes.

Stack a few of these sort of considerations up, and before long Fermi's "paradox" stops seeming very paradoxical.

Great filter might involve harsh tradeoffs like "no stupidity allowed". Do you really want to know it?

Speaking of "great filter", I often wonder about the hypothetical case that we live in a fragile universe.

Whatever the first civilization is to cause something like vacuum collapse could destroy the entire universe at the speed of light. Maybe it's already happened somewhere and is currently propagating our way.