I agree. Most people aren't leaving because it is a subscription-based game. They are leaving because it is a subscription-based game that no longer has new content for them. All the other stuff about it being unfinished etc I think people could live with if there was reaonable content updates to keep them busy or at least the promise of regular, future content updates to give them a reason to hang on even when content seems thin.
Making it free will get people back for a little while, but not for long. Free or sub-based, the same problem remains: not enough to do, so why stick around?