How come everyone assumes aliens are our better and not just swamp slugs of some type swimming around in a cosmic quagmire who know nothing of us?-)
Some theories actually exist that we may be the most advanced civilization out there — at least within our galaxy. These are based on things like the age of the galaxy, how many cycles of supernovas must occur for complex elements essential for life to exist to exist in sufficiently high levels, etc.
If you look at the constituents of our biosphere, there are fairly common but with a few notable exceptions.
In other words, life is probably all over the place. But those few exceptions mean advanced life might be very rare. And again, we might be the most advance. How’s that for a scary idea?