So, doctrine is important to the organization, but unquestioning loyalty is really how they hold people. To me, the folks most likely to leave are ones who really understand the doctrine.
For the rest, they're happy not understanding everything but they're not willing to make too many sacrifices. Its a tightrope and eventually, they're going to fall off.
These are very good points. I have noticed throughout my years in the org, that many of the most ardent defenders and apologists for the org are those who really don't understand the deeper doctrines very well; and have no idea how such doctrines were formulated. I fell into this camp. When I actually began to do in depth research into various doctrines (Faithful Slave, etc.) I began to see through the smoke screens.
Most Witnesses are happy to let someone else do the hard work of thinking for them. Despite it's handicapping effect; it affords a certain level of comfort for people who need to have their reality sliced and diced into nice, neat, little symmetrical categories.