One problem I see with this article: for us to detect the aliens, they have to be aiming their signals directly at us. Broadcast signals don't carry very far in space, it has to be a tight beam. And that means the aliens have to already know we're here. Or they have to be aiming powerful beacons at all the hundred billion star systems in the galaxy, and that's significant resource to spend on something that's never going to pay back. Even if the signals do reach an alien civilization, it's going to take thousands of years before they can possibly get a response. And they have to be listening for it by that time, which means a hundred billion radio telescopes aimed at all those systems. It's a fool's game. While I love the idea of SETI, I don't see how it can possibly work.
But there's more: even if there are billions of planets with life, that doesn't mean that there are that many civilizations. Evolution does not have a direction towards intelligence and civilization, it has a direction towards survival. The evolution of technological intelligence could be extremely rare. I think there will be plenty of life out there, but I fear most of it will be very primitive, single celled prokariotes. It took Earth a very sizable chunk of its history to even get to eukariotes, and then to multicellular life. Maybe, on any planet with slightly less favourable conditions, that evolution would take 10 times as long, and therefore never be finished within the lifetime of the planet.
Are out conditions more favourable than elsewhere? We have no idea of course, but none of the exoplanetary systems we've found look exactly like ours, and many look completely uninhabitable (hot Jupiters and such). We have an unusually oversized moon that creates big tides, allowing sea creatures to slowly adapt to land. Without big tides, maybe life would remain limited to the sea.
I think there are a lot of subtle filters that we already passed, that tend to get ignored. It's possible that intelligent civilizations might be incredibly rare. And maybe that's for the best, because if they're common, we can be almost certain that we'll never be able to visit them. If it were possible, they would have visited us a million times over in their billion year head start, and we're not seeing any evidence of that.
Then again, maybe the evidence is there, and we just haven't found it yet.