I'm not at all suggesting that the Great Filter is a real thing. I consider the other main solutions of the Fermi Paradox (Alien life being too alien, Simulation Hypothesis, Dark Forest, Zoo and other) just as intriguing!
Great Filter is neat because it bundles many different solutions together into one class. Any solution saying that civilizations in the Milky Way are incredibly rare is basically a variation on Great Filter.
>why should we assume anything about our ability to determine life beyond our Solar System?
It isn't farfetched to assume that sufficiently expansionist/numerous Kardashev type 2+ civilizations should be easier to detect from Earth than bacteria on Venus.
Well, that depends on how you define "the Great Filter" I suppose. For many it's attempting to explain why intelligent civilizations are rare, rather than why Kardashev type 2+ civilizations are rare. Of course, if you strictly define it as "the thing that makes it look like intelligent civilizations are rare" I guess that would also work... I just rarely get the impression that this is what people are referring to.
I see. Well, we cannot say whether life or intelligent life is rare. There could be millions of worlds with civilizations like ours and it wouldn't be that strange we missed it.
However, it does seem that the Milky Way is not collonised (not even the other galaxies as far as we can tell), and if that's truly the case, then it would suggest that there is some kind of filter barring all civilizations from ever doing it.
I consider interstellar travel not ever being viable a legitimate filter.
Of course there is a plethora of other solutions as well.
Great Filter is neat because it bundles many different solutions together into one class. Any solution saying that civilizations in the Milky Way are incredibly rare is basically a variation on Great Filter.
>why should we assume anything about our ability to determine life beyond our Solar System?
It isn't farfetched to assume that sufficiently expansionist/numerous Kardashev type 2+ civilizations should be easier to detect from Earth than bacteria on Venus.