I’ve always felt that the reason we haven’t heard from aliens is because they know New Physics and they use it to communicate. Given how much of the universe is made up of dark energy, dark matter and other unknown physics, it seems reasonable that there are significant discoveries to be made which could perhaps be exploited.

I mean let’s say we discover a new, non-electromagnetic way to communicate reliably over vast distances using some kind of low power, high bandwidth signalling system. We’d abandon EM in a geological heartbeat. In cosmic terms we would emit a wafer thin EM shell just 150 light-years thick - and then we would fall silent.

So basically I just think we don’t know enough physics yet. We are perhaps a few discoveries away from being able to listen in on alien conversations.