WT February 2017 par.12, p.26:
" The Governing Body is neither inspired nor infallible. Therefore, it can err in doctrinal matters or in organizational direction. In fact, the Watch Tower Publications Index includes the heading “Beliefs Clarified,” which lists adjustments in our Scriptural understanding since 1870. Of course, Jesus did not tell us that his faithful slave would produce perfect spiritual food."
So since 1870, the WT has just been muddying its way through the Bible all on its own, trying to figure out what it means.
What about other religions, does God speak to them, contact them?