There is a huge difference between trail maintenance and trail alteration. In my view, trail maintenance is about going out and clearing trails and repairing features (i.e. downed trees, installing water diversions, and repair of berms and ruts). Everyone should do trail maintenance and no one should complain unless they are out there actually doing said maintenance.
Trail alteration is a totally different animal. I'm talking about rerouting trails and removing, modifying, and installing obstacles, challenges, and features, especially when those actions change the previous character of the trail. Over the last several years this has become a major complaint for a lot of people, especially with IMBA's design standards becoming more and more prevalent. Its one thing to build an entirely new trail to IMBA specs, its wholly another to take an existing trail and completely regrade and reroute it to remove obstacles and reduce the grade. Soooo, when people see this they aren't complaining about maintenance, their complaining about alterations, and they have a legit point in many cases. Same goes for someone complaining about someone putting in a sketchy drop or jump in what was developed as an easy/moderate trail. What is the point of going to trail building sessions when its quite clear that the decision makers only know and appreciate one way of building and will never ever take the position of hey, thats an expert level trail, lets leave it alone.
Bottom line to me: Its sad that we live in such an awesome state for riding and yet don't have a single (legal) trail that can match up with even a moderately difficult black diamond trail just a few hours north in Northern Washington and BC.