You touch on a couple of issues. The first is that civilizations tend to be short-lived. There are only really two ways out of this: they wipe themselves out o

You touch on a couple of issues. The first is that civilizations tend to be short-lived. There are only really two ways out of this: they wipe themselves out or they somehow "transcend". "Transcending" is a trope of sci-fi (eg David Brin's Startide Rising series, the Iain M. Banks Culture series) but it's very handwavy. We really have no conception of what that might be. Living in the quantum world? Higher dimensions? This is really the sci-fi version of godhood. As for wiping ourselves out, that's becoming increasingly harder. We are currently in the latter stages of it being possible to wipe out humanity, despite all the talk of Armageddon. If would really take a large cosmic event at this point. I'm talking the Earth being hit by a truly massive object, the kind that puts the dinosaur-killing asteroid to shame. Things like nuclear war, biological wars, disease, etc could be truly devastating but kill every last one of us? Easier said than done. It would really take making the Earth truly uninhabitable. Now another K2 civilization currently has the ability to wipe us out by virtue of the huge amounts of energy they have. Two talked about forms are the Nicoll-Dyson beam (quite literally, turning the energy of a star into something that would bather the target in radiation) and relativistic kill missiles. Barring some major disaster, in 1000 years this is unlikely to be the case, particularly if we reach other stars. Of course there's something we might not be able to conceive of but this too feels very handwavy. The second thing is the Fermi Parai Paradox itself. You can argue that not every civilization goes the Dyson Swarm route or even continues to grow. Some might fade into irrelevance. There are a bunch of possibilities. But we're not concerned with what's likely or expected. Imagine if there were 5 civilizations in the Milky Way. What are the odds that none of them become K2 civilizations and surviving long term? There's some nonzero possibility. But what if there were 1000 civilizations? As N gets higher the probability that zero of them become long-lived K2 civilizations starts approaching zero. We look around us and see... nothing. That doesn't mean there's no one out there but it looks increasingly likely the galaxy isn't teeming with spacefaring life. I, for one, think it's most likely that we are the only spacefaring civilization in the Milky Way, at least within our light cone (which means much the same thing).