Regarding Luke 17:22 and the length of the generation and the WT's failed predictions, the main reason why the WT's predictions haven't come true and why the WT keeps changing their doctrines is that the foundation for the WT's teachings is seriously flawed. That foundation is the Bible, including the NT, even the Gospels. To varying degrees the writers of the Gospel accounts disagreed with each other. One of the reasons Luke's gospel was written was to explain why Jesus hadn't yet returned, like the WT changing their definition of the generation. See https://www.npr.org/transcripts/124572693 ("Author Interviews
< Jesus And The Hidden Contradictions Of The Gospels"), in which Bible scholar Bart Ehrman is interviewed.
Part of the interview says the following.
"Professor BART EHRMAN (Religious Studies, University of North Carolina; Author, "Jesus, Interrupted"): I think it's important to know that each of these authors of the New Testament had a different message. What people tend to do is - allied the various teachings of, say, Matthew, Mark, Luke and John so that if Matthew portrays Jesus in one way and Mark portrays him in a different way, what people do is they conflate the two accounts so that Jesus says and does everything that he says in Matthew and in Mark. But when you do that, you, in fact, rob each of these authors of their own integrity as an author."
In the interview Ehrman says the following about Jesus being an apocalypticist.
"Well, Jesus didnt think there was going to be a long haul. So when people say that Jesus was a great teacher of ethics, I think thats absolutely true.
But one needs to understand that his ethical teaching is rooted in a completely different worldview from the one that most people have today. For Jesus, the reason that you needed to start following God and doing what God wanted you to do the reason to behave ethically - is because the judgment day was coming and it could be sometime next Thursday. And you need to be ready for it by behaving in the ways that God wants you to, so that when this cosmic judge of the Earth arrives and catastrophe starts happening, youll be on the right side. And youll be able to enter into this good kingdom that Gods bringing because if you disobey God and you're acting badly, youre going to be destroyed when this cosmic judge arrives.
...
Prof. EHRMAN: ... Theres a wide range of opinions about who Jesus is. And in the last 20 years, there have been people who've wanted scholars who have wanted to redefine Jesus so that hes not an apocalypticist. But the majority of scholars dont agree with that. But there is something to be said about Jesus as a social reformer and somebody who promoted egalitarian principles. But the reason is not the one thats sometimes given. The reason Jesus wanted to reform society, and supported things such as the roles of women in society and such, is because he thought thats what the kingdom was going to be like.
In the kingdom, theres not going to be inequality. Theres not going to - oppression. Theres not going to be war. Theres not going to be there's going to be equality of all people. And so you should start implementing the ideals of that future kingdom in the present.
... if you actually situate to Jesus in his own historical context, this is the sort of thing that a lot of people expected was going to happen - just as people today. I mean, in evangelical Christian circles today, there are many people who think that Jesus is coming back - and they dont mean that metaphorically. They think that Jesus, literally, is going to come back. And I think they had their predecessors in the first century.
...
Prof. EHRMAN: Yeah, thats right. And, you know, the Left Behind series sold far more copies than The Da Vinci Code.
(Soundbite of laughter)
Prof. EHRMAN: As hard as that may be to believe. But in fact, it did. And whats striking is that this idea that we are now living at the end of time, and that current events are showing us fulfillments of Biblical prophecy - exactly the same thing was being said 10 years ago about things happening 10 years ago -and 10 years before that, and 10 years before that, and 10 years before that. You can go all the way back in Christian history, and every decade thought that they were living at the end of time, and that the prophecies were being fulfilled in their own day.
You can trace this back through the Middle Ages, all the way back to early Christianity. In fact, you can trace it back to the apostle Paul and the historical Jesus. People have thought this from day one. And what I sometimes tell my students is that you can say two things about these people who think that the end is going to come within their lifetime. One thing is that every one of them bases it on their certain interpretations of the Bible especially, for example, the Book of Revelation. And the second thing you can say is that every single one of these people has been completely wrong.
The point, though, is that this view actually does go back to the historical Jesus. Jesus also predicted that the end was going to come within his generation and, of course, it didnt."
Regarding discovering contradictions in the Bible, Ehrman says the following.
"And I got to a point where I started realizing that I couldnt reconcile all of these discrepancies. And you know, many of them are just quite clear contradictions - some of the ones we havent actually talked about on the program so far.
But I got to a point where I realized there are contradictions. And once I said that, it had a serious effect on my faith because my faith was rooted in an inerrant revelation from God. And I began realizing that, in fact, this revelation was not inerrant. This revelation, in fact, had errors. And once I started seeing errors, I started finding them everywhere."
See the book called The Bible Against Itself: Why the Bible Seems to Contradict Itself by Randel McCraw Helms. It is an excellent book. In April 2019 I checked it out from the library of the university which I had graduated from in the 1980s. The following is a quote I wrote down from the Introduction of the book (ISBN 0-9655047-5-1).
"... the Book of Jeremiah had to endure massive reinterpretation by the author of the Book of Daniel when its predictions seemed wrong (Dan. 9:1-24). Then Daniel was itself reinterpreted by the author of 2 Esdras when its predictions failed, and then again by the author of the Gospel of Mark (which was in turn reinterpreted by the authors of the Gospels of Matthew and Luke), and then one last time by the author of Revelation. Apocaplypse is never now, but only soon to come, and then still soon to come. Predictive prophecy, like the Bible, is self-destructing." This book makes an EXCELLENT case that much of the Bible deliberately contradicts much of the rest of the Bible!