My understanding of this, is that the signal intensity required to be detectable on earth means that messages would have to be intentionally beamed at earth with ridiculous energies. It seems unlikely that any significant fraction of civilizations would be doing this toward any sufficient fraction of sky.

If we were trying to detect a duplicate civilization to ourselves, (assuming our signals had propagated further than ~100 light years) we're certainly not producing signals of sufficient intensity that we could detect our own signals with the detection equipment we're using.

It also seems like there's likely to be a lot of pressures on a civilization to become more energy efficient for a long time before progressing to expensive technologies like dyson spheres and whatnot. I still think such things are our best bet for detecting ET civilizations.