what I have noticed is the breed specific rescues are going over the top with requirements. Like the Aussie rescue that requires 1 full fenced acre per dog. Now I know aussies are high energy, I had 2 and when my older one passed at 17, I went to a rescue rather then buying one. They turned me down for not having at least 2 acres for them to "romp in." But they completely agreed that my pup was in great help and got lots of excersize. So a knowledged and willing austrailian shephered owner was turned down. Most of the rescues would rather keep the dogs and continue getting their donations and tax deductions then adopting them out to good homes.
PS. I now have a minpin from a more willing rescue and my other aussie who is now 11 and even the Vet says she is in great health and does not even show her age.