We've only barely detected that planets exist outside of our solar system fairly recently. Our observations are mainly limited to the general size of them, e.g.

We've only barely detected that planets exist outside of our solar system fairly recently. Our observations are mainly limited to the general size of them, e.g. 1 Jupiter width, 2 earth masses, etc. Telescopic images of other stars in our galaxy are just a couple pixels. We're essentially blind but saying there's nothing to see. We don't yet have the technology to really observe what's happening in our galactic neighborhood. We don't even know what's going on under the atmospheres of the gas giants in our own solar system and it's mostly speculation. If another planet had a pipeline linking their planet to a star for pure plasma energy, we couldn't even observe that with today's tools. Another planet observing earth for intelligent life using our standards would also conclude that there's absolutely nothing here. Artificial lighting is under 200 years old, leaving little in the visible spectrum as an obvious sign of intelligent life for anything over 200 light years away. They could easily brush off oxygen/CO2 production as some sort of natural process. They could also conclude that the idea of life existing on earth for hundreds of millions of years is insanity, because clearly earthlings have planetary rodeos where we'd drag planets around for fun or we'd be using the methane on our gas giants for sustenance.