he substratum of all JW teachings is that humans would bring only ruin if they try to rule themselves without taking God’s will into account. And when the ruination reaches its climax, God would replace the present kingdoms (the real ruler of which is the greed of those who use technology) with His Kingdom; hence JWs has the caption: “THE WATCHTOWER announcing God’s Kingdom.”
All other teachings have only secondary and supportive role, hence change in them would not matter.
I think it does matter as the good news as preached by Jehovah's Witnesses included the time limit of a generation. Those that saw the beginning would see the end. This did not occur and this was changed. My view is that the good news cannot be changed.