When I was teenager going DtoD I would defend JW doctrine to vicars and other Ministers of religion, not brilliantly I bet, but to the point where we agreed to differ.
I doubt many adult JW's could defend present doctine in that way, if they even know what it is.
It was a simpler and more genuine faith that was encouraged when I was baptised as a pre-teen (by a few months), I was baptised vowing that I would serve god as he explained he wanted me to through Jesus and the Bible, we did not defend an Organization, but our own faith that we had proved to ourselves from the Bible, albeit that our understanding of the Bible was warped by the WT's input.
In those early days I don't remember any saying that a teaching was "too deep" to understand, such expressions came later when things got more and more convoluted.
I can completely relate to that. Many young people my age couldn't defend their faith.
Alec