100,000 years of intelligent space-faring civilization is a long time by comparison to us. All we've got so far is a few decades and we've come pretty close to blowing ourselves back to the stone age on a couple of occasions with all the new-fangled weapons we developed along the way. When you think about it, it wouldn't take that much to set this whole place ablaze, and it'll only get easier as more countries get bigger weapons. Some nutcase launches a missle, which causes the recipient to launch another, and then back and forth to destruction. Maybe we're coming up on a hump that advanced civilizations have trouble getting over... once every country has nuclear weapons. Smart enough to develop the technology, but still to stupid to use it correctly.
There swarms of tiny robots all over the galaxy (this is the origin of dark matter), and when they detect abnormal radio signals coming from a star system they start to converge on that star system. We have been producing radio signals for about 100 years so they are well on their way to us.
When enough of them arrive, they descend on the origin of the radio signals and destroy all organic life.
Yes...your point is well-taken. Has any advanced civilization been able to make it past the WMD stage of development? It would explain why no one has shown up so far.