King Saul was rejected for going beyond what is instructed. (eg. He started preparing for the battle by offering sacrifices as Prophet Samuel did not turn up even after the stated one week time (1 Samuel 10:8 & 13:8); He also did not FULLY carried out to kill ALL the Amalekites).
Would not same principle apply in the case of JWs also when they have gone, many times, beyond what is written? Whenever they made changes in their teachings (even in many of their core-teachings), they did go beyond what is written, or acted at lease without having FULL knowledge!
Ironically, constantly changing teaching and a God who “never changes” can never be reconciled! (James 1:17)