Atmospheric tags for life invalidates Dr Sagan’s objection to visitation. An advanced species would have known we’re here long ago and could have sent exploratory probes. Those would have justified ships probably robotically staffed.
I would like to think that there are aliens out there watching us, but that would be very arrogant of me. I do not think we are smart enough to be of interest, the planet though that is a different thing. If they wanted the planet we would all be dead, since we are not they are not out there wanting our planet.
If life like ours is common and interstellar travel is practical, yes, they've been watching us all along. Alas SETI keeps coming up with nada, and some very promising avenues have been explored. At this point the rare Earth hypothesis is looking better all the time.