There are billions of galaxies though, so even if we are the only planet out of billions in our galaxy with complex life, there could still be billions of civilizations out there!
For that matter, the typical planet with life could be too large and have too thick an atmosphere for space travel or astronomy and thus never have any idea the rest of the universe exists. That wouldn't necessarily mean life was limited to single cells.
For that matter, the typical planet with life could be too large and have too thick an atmosphere for space travel or astronomy and thus never have any idea the rest of the universe exists. That wouldn't necessarily mean life was limited to single cells.