i feel this is too hyperbolic in the wrong direction. there is clearly more beyond our current knowledge of physics, so why is it beyond the realms of reality to assume that something in that subset of all knowledge is useful? we didn't even know of the possibility of gravitational waves a century ago and just confirmed their existence. so why is it reasonable to say they couldn't possibly be useful for communications?

in dealing with the eventuality of alien civilizations, we must open our mind. it is certainly probable they communicate in ways we can't understand, even if they are simply evolutions of our current communication methods.