My point to an elder was that the Israelites had the 10 plagues, the cloud of fire that led them, the parting of the red sea, and the manna they received each day to remind them who was leading them. Jesus gave signs and miracles. Where are these signs with the WT? Only 1 "prophecy" has come true and they even prophesied wrong about that one. Since 1914, they have been wrong about every other "prophecy".
The only thing he could point to was correct understandings of core doctrines (hell, trinity, ransom) and the preaching work. The core doctrines we believe are correct because that's all we've ever been taught and the preaching work is experiencing diminishing returns.