I find myself thinking that the existance of Dark Energy/Dark Matter is the solution to the fermi paradox. there is some kind of energy creating system which creates dark matter. This matter is no good for normal matter so it is transported far away from stars/galaxies and dumped. This would probably be true if we could create a physics model that can explain like 1% of Dark Matter occurring naturaly. Then we just assume that other species have discovered how to create a ton of energy with Dark Matter as the by-product. We haven't been able to observe them for the same reasons our telescopes can't see the New Horizons spacecraft out by Pluto, just too small. And as far as observing communications. It's likely that all true interstellar communication on frequencies we could understand are sent with a targeted focus, like a laser, rather than a blast. Think of all our deep space equipment which has their uplink bits pointed toward earth.