It is highly likely that ET civilizations will use technical means of communication which may be far beyond our capabilities, but it should also be made clear that exploiting the "traditional" SETI communications medium, microwaves, is certainly not a waste of time.

The very high S/N ratio of waterhole microwaves, as well as the transparency of the interstellar medium to them, plus the inescapable fact that all astronomically sophisticated cultures will be monitoring these frequencies for other reasons; tells us that this is a potentially fruitful SETI strategy for us, and them, to follow.

We should also keep in mind that the first SETI signals we receive will likely be deliberately designed as effective beacons, not as efficient datalinks. If ETI is trying to get someone's attention (as opposed to trnsmitting routine signal traffic that we accidentally stumble upon) they will probably use smoke signals and drumbeats.