Protestants accept their Canon on the basis of Tradition.
And The JW`s blindly followed what the protestants accepted simply to be different and apart from the Catholics.
How could all scripture be inspired and beneficial when not all scripture had even been written when this scripture was penned ?
What about all of the other "scriptures" that were written that have not been included in the Bible that imperfect human men (not women) deemed was not to be included in the cannon ,judged by their human imperfect wisdom ?
On the other hand they keep changing their beliefs so often how does any JW keep up with their core beliefs?