One measure of the advancement of a technology is how little energy is wasted in normal operation. This includes communications. It's entirely possible that a highly-advanced planet would not radiate enough energy to be detected at great distances. Think fiber optics.

This is of course assuming they are even using radio waves for communications. Five hundred years ago nobody could have conceived, even imagined, a way of transmitting sound across a distance other than by shouting. A genius of the time might have imagined immense bullhorns at city walls to enhance this.

Transmitting information by light worked as far as the horizon. Signal flags, or the kind of signal fires that figured so dramatically in the last Lord of the Rings movie. In the Terry Pratchett "Discworld" books, entrepreneurs have set up a network of ingenious mechanical semaphore towers across the country to transmit data.

Radio wasn't even a gleam in anyone's eye. Completely off the mental map.

We may be operating in the same mode with advanced ETs. And, considering the very short time we've had a technological civilization compared to the age of the planet, or even the history of our species (radio is only how old?) almost all civilizations that haven't destroyed themselves must be more advanced than we are.

There may be other civilizations that are currently crossing that short electromagnetic bridge between signal fires and "subspace transmissions" or "ansibles," but they are probably quite rare.