One of their biggest self-authenticating claims has to do with their preaching work.
10 They are fulfulling Mt 24:14 and they are the only ones doing so.
However, even when I was at my peak as a zealous, believing JW (late 80's / early 90's), I lamented the way the preaching work was carried out. I really believed in it and wanted it done in an appropriate way to an appopriate degree. However, it wasn't.
I wanted to use the Bible and have discussions, but I was forced to place magazines using brief presentations. Those magazines were filled mostly with fluff. There might have been a few good sentences or sometimes an entire good article in some of the mags, but they were often buried in fluff.
I found that most JWs were simply not qualified to do such an important work. I was often cringing when working with other JWs as I observed their ineptness.
Now, the preaching work is almost non-existent. It is still mosly fluff and it is carried out by JWs who are mostly not qualified, but, now they are much less qualified than they were a few decades ago. They are much more ignorant of their own doctrine than JWs were a few decades ago. They lack the boldness that a lot of JWs used to have. They run from deeper questions and challenges now. The quantity and quality of the preaching work have decreased. It is, at best, a faint whisper now - puny and weak.
If JWs were who/what they claim to be, having the one and only way to salvation for billions about to be violently destroyed (according to their doctrine), their preaching work should be like the shouts of the Israelites marching around Jericho on the seventh day or like the warning work of Jonah in Nineveh. However, the preaching work of JWs is nothing like those things.
I remember hearing/reading when I was in JW Land that JWs had progressed greatly beyond the days when they used phonographs to preach. Now, though, they've gone back to the same method, just with updated technology; they simply point people to their website or use recorded videos.
So, the whole world is about to be violently destroyed and JWs are providing an appropriate warning??? Hah, we getter better/clearer/stronger warnings in our area for a local thunderstorm. If JWs are who/what they claim to be, they are going to have blood on their hands. They are nowhere near close to fulfilling Mt 24:14. They don't have a clear message and never have. Clarification: Maybe they had a clear mesage, but they never presented it clearly. By far, most people on earth have no clue what the JW message is.
No, their ineffective preaching work does not authenticate them.