I know that Getting Things Done is really for people who have already made up their mind to get things done. David Allen tends to assume that people are not resisting "doing stuff" because of procrastination or laziness - his system is not really for those folks.
However, I think that the major issue in getting things done is motivation. Those with high energy and desire tend to take over in most situations. They may not use GTD but they figure out something that will work.