Wait a moment, maybe I understand wrong (English is not my first language) but I understand that you said that the Great Filter is the reason why we don’t see them and point out 3 possible points.

I dispute your first point to be not really an explanation or an option since saying “never feasible for any civ, no matter how advanced” just seems to be a too harsh limit on what a civ could do, which looking at our past history seems an unreasonable limit.

My friend, that’s exactly my point. That is, they’ve had enough time to show up but they are nowhere to be seen.

Your point seems to be that since there is the Great Filter (btw, to be proven) then there is no one else out there.
You exclude way simpler possibillities like the option that a civ just a couple centuries ahead of use could already be colonizating the nearby stars, they just are 1000 LY away so we cannot yet see them (assuming we even know what to look for).