Virtually every J.W. will gladly tell you that Matthew 24:14 proves that only they are God's true people/religion, because they are the only people preaching the good news worldwide today. Crucially, they double-down on this lame bet by adding that their worldwide preaching proves another WTBTS teaching, namely, that we are living in "the last days." (the same last days Russell predicted over 140 years ago!!!!!)
In every instance in Matthew chapter 24 where Jesus used the term 'you', he was referring to his 1st century disciples (including their contemporaries) who had asked him the questions in verse 3. Verse 34 confirms this fact when Jesus said 'this' generation – not 'that'. (future)
1) At verse 14, Jesus revealed what 'this' generation would witness before the end came, namely, that the good news of the kingdom would be “preached in all the earth.” (Greek - οἰκουμένη - "the portion of the earth inhabited by the Greeks, in distinction from the lands of the barbarians; the Roman empire, all the subjects of the empire" - Strong's Lexicon)
2) Scripturally, Jesus words proved true for 'this' generation, as Paul's words 28 years later confirm; “...the hope of that good news that you heard and that was preached in all creation under heaven.” (Colossians 1:23)
3) Jesus then told his disciples ('this' generation) that a 'great tribulation' which would never occur again, would then unfold. That tribulation came & went between between 66-70 C.E.
J.W.'s should be comforted to know that Jesus never said anything about that great tribulation having “a greater fulfilment” in the future. The elders should be able to explain these contradictions to the flock.