I've always percieved the 2 most important doctrines by the society as:
1) The Bible and Gods' Spirit are no longer sufficient to adequately direct Christians after 2 melliniums, requiring a 3rd party aka...F/S
And the 2nd fits nicely into the first
2) Upon the closing of the Kingdom of the Heavens by Rutherford in 1935, they in effect denied Jesus' role as mediator to the rest of humanity thus substituting themselves as quasi mediators eg... sole channel God is using.
As a result of this 'coming into Jehovahs' organization' is substituted for belong to the Christ, his 'body' and thus the need to be baptized into the organization rather than into Christ. What had started out decades ago as a means has become the end for the pursuit of salvation in the religion.
This in my opinion, is Idolatry, pure and simple.
Allen