I disagree. A person's involvement is not related to their level of moaning in my experience. Some of the most productive trail building people in Flagstaff are among the loudest complainers, which is good because it serves to get attention and funding. Plenty of people complain and do nothing as well. That results in changes too, for better or worse.Actually it's the other way around. The people that * and moan are the rippers that are too busy riding to get involved. It's easier to complain.
Regarding your point that you can't make everybody happy, I had this same discussion with the guy responsible for much of Prescott's trail progress in the last decade and his response was, "I don't engage with the public". The crickets will always chirp no matter what you do.