Maybe the reason why we haven't encountered alien civilizations is simply that we are the first in our region?
If you think about it you need a second generation start like our Sun because the first lot of Stars needed to go supernova to generate the heavier elements and compact our star system into something like it is now along a nice plane with larger gas giants and a "cloud" of water bearing asteroids circling far out. The earlier second generation stars also had a problem where earlier in our galaxies history there were more pulsars and O-type stars that could have killed life by sending jets of high energy radiation our way.
Next you have to wait for the planet to form and then get water from the stabilization of larger gas planet orbits bringing in the water bearing asteroids. Then you have to wait for the planet to cool, the water to seep down and create some sort of active continents with plate techtonics. Then you have to wait for the iron to settle in with the water, first life to start producing oxygen in the atmosphere, and evolution taking its long course to make something that can make useful technologies and contemplate the universe.
Could just be that we are the first (somewhat) intelligent life around.