Plus, why would an advanced civilization that has already understood the value of energy waste this kind of energy trying to contact us?

- If they are advanced (+civil), then they would have seen a critical development that this became a necessity, rather than preference.

- They may not be civil: not caring what energy they waste. Advanced but not responsible beings.

- They may be doing something for themselves, leaving traces to different directions. We may have stumbled on a construction site. Nothing of value for sending a response. Would you beam a response to reaction site of a supercollider? In case you did, would you get a "message" back? I doubt it.

- Most probably: interference.