I am not entirely sure this question is relevant to what the JW religion actually "is".
The JW religion is a social meme with very specific attributes that allow it to exist. One of those principal attributes is the shunning policy. If this were removed, the product that is the JW religion would either not exist, or would be something very different from what we know. The whole of something is not really the sum of its parts, but rather the product of the interaction of those parts, along with the environment it operates within, (society at large).
I doubt very much I, or most here who have been a JW for any part of adulthood, would have been one long without the shunning policy. As a result, the organization manages to keep members, (therefore exist), because of it.
d4g