I disagree.
RMS is (much like Joseph Ratzinger, for a different religious movement) much better as a chief theologian, theorist of doctrine, and internal enforcer of and exhortationist to doctrinal purity within the Church than an ambassador or evangelist to those not already deeply committed.
Literally no person, anywhere, regardless of background, history, technical capability, history with free software, networking or speaking ability, is capable of acting as ambassador for the Free Software movment in the same capacity? Only RMS?
You realize he's a mortal human, right? Because if your premise is that no one else can ever be worthy to replace him, your conclusion must be that the movement will die with him.
Being the person who comes up with an idea doesn't have anything to do with being good at selling the idea to other people.