I don't think the quality control/process changes has only lost us former contributors.
I see many more cases of different people submitting patches. The process is now well documented and the same for everyone. That is in contrast to the old system where there were people with CVS commit access, who could easily get their changes in, and everyone else, for whom it was almost impossible to get your changes in.
Evey release, Dan Poltawski does a count of the number of different people who have contributed at least one fix, and that number is tending to go up.