Paul also said in Galations that anyone coming to them with a different message, or good news, even if it were an Angel, that one was to be ignored, the Gospel (Good News) was "Christ Ressurected". Thats it.
So anything that the WT/JW's wish to add to that, i.e paradise earth, only 144,000 going to Heaven, a class of people called the FDS,no blood transfusion, Armageddon etc etc is to be rejected, and yet these are the very things they expect you to go out and preach !
The actual Good News hardly features in their literarure and teaching, in fact they seem to think it would be a good thing if Jesus faded away and just left their Governing Body in charge totally, especially of the coming Kingdom.