given the distances involved and what we know about the speed of light, an alien civilization would have had to develop a very long time ago in order to send signals that we would be able to detect today.
The Milky Way is only 100,000 light years across, which is a blink of an eye in geological time.
It doesn't matter. The point is that the only local-galaxy civilizations we would fail to detect for being "too far" would be those that were born only yesterday, on the timescales involved. All things being equal this should be an irrelevant fraction of the total.
A different matter is "too short lived", which is taken into account in the Drake equation (the last factor, L).
The Milky Way is only 100,000 light years across, which is a blink of an eye in geological time.