And therein lies the root of the problem. God did not get "this group" and so the preaching work is null and void, just a total waste of time. They took it on themselves to declare that they were God's special people, but their record says otherwise.
I personally think that God did use the WTS at one time, but not anymore, not for decades, as I believe it has been judged and rejected as unfit. I think God has let them to themselves.