oh Fermi and your paradox
Two interesting articles on the Fermi paradox state: one, that civilization burns itself out via industrialization-fueled climate change; and two, that ignoring the discussion isn't helping us mature to the point that we can even contemplate moving into the stars.
I find the question of our missing galactic neighbors to be one of the most interesting out there (as it were). I personally like the approaches that use a model to try to determine how other space-faring races might reach us, such as empty quadrants. I like these because it seems to make people think through ramifications as they're working out a model, rather than simply tossing out stuff like the "zoo hypothesis" or "a super-predator is wiping out civilizations as they emerge" or "we're living in a computer simulation" or "the aliens are sleeping". Here's an example: I could just as easily claim that the problem is theropod dinosaurs.
the trouble with theropods
Let's say an advanced alien race came to Earth 230 million years ago. They would have found it teeming with theropods. That's not a great environment in which to start a new colony if your bodies are made of sweet sweet meat. So maybe they checked in every 50,000 years to see whether conditions had improved. But the problem kept persisting: the early Eorapters eventually gave way to Ceolophysis and then Ceratosaurus and then Allosaurus and then to T-rex. You can't live with theropods, and they were far too numerous to hunt down. By T-rex's time, there had been theropods for 170 million years. That's a lot of once-every-50,000-years visits. Frankly, it wouldn't surprise me if they'd just gotten fed up in visit 3,400 or so and dropped an asteroid on poor old Earth. And then they came back once more only to find the place still teeming with theropods (in the form of terror birds). At this point, if I were them, I'd put up a warning beacon saying something simple like, "warning: therapods".
My point here is that theropods would have kept any visitors at bay virtually forever. Also, that theories that might sound plausible but are of course unprovable don't tend to help.
what to do about it
I plan to continue to write first-contact fiction and hope that we can get our act together as a species before some aliens do finally show up and are too horrified by what we've made of Earth to make contact. E.g. fixing global warming, stabilizing our population, building more tools to watch for aliens, and maybe stop wiping out animal/plant species, to start.
Perhaps it will feature the discovery of a "warning: aggressive apes on amphetamines" beacon.