Our signal for oxygen and other bio-signatures is so much stronger than the signals we have been sending recently and it's been going out for...quite some time.

Maybe they found Earth already and they just find it boring: "yet another planet likely filled with idiots"

I mean, the Great Oxygenation Event is ~2 billion years in the past, and the Cambrian Explosion is only half a billion years ago. If intelligent, space-faring aliens checked it out, there's a 75% chance they arrived while the most interesting thing on Earth was, well, I can't think of anything that wasn't "technically before the Cambrian but like, only by 50 million years". Fungi?

We should look for oxygen-rich atmospheres, but we need another signal before we jump in a rocketship and go looking for someone to talk to or eat.