However, I'm skeptical of there being any intelligent life out there that we could feasibly communicate with on any useful timescale anyways, so I don't necessarily disagree with you. I just don't think this argument is inherently sufficient.
If they are that advanced, would they care about stealth or strategy?
This is also assuming they would even have the same values as us. We send probes and signals out, clearly we want to make contact, so they may see no problem with not using stealth, especially if it saves resources for them by being a little more obvious but still avoiding contact.
That's a fair bit of time for the possibility of some other life within our galaxy to detect atmospheric signs of life supporting chemicals on our planet and to send a probe to investigate.
I don't think it means aliens have visited or sent a probe but I think it is possible.