So to clarify, do you agree the following events happened/occurred/were done/took place in the disciples’ 1st century generation: persecution, famine, war, earthquakes, lawlessness, those falling away from the church, the gospel being preached to every creature under heaven, Jerusalem and the temple destroyed, the servants gathering the good and bad into the wedding feast, the son of man coming in the clouds (matthew 26:64)?
Some of those things you listed, such as falling away from the church, while that may have been true to a degree, though I don't know if it even was true to a degree, it certainly wasn't true on the scale Paul is meaning in 2 Thessalonians 2:3, though. He called it a great falling away. As to Him coming in the clouds in the first century, in any sense, I totally disagree with that.
He left in the clouds of heaven and returned to heaven in the clouds of heaven, which BTW, shows that literal clouds are obviously not meant, but He never came back to the earth in the clouds of heaven, in any sense. He does that in the end of this age, comes in the clouds of heaven and that in the first century that was not in the end of this age. Therefore, while it's on my mind, that is something that was never fulfilled in the first century, Him coming in the clouds of heaven in power and glory, and that Jesus said all must be fulfilled before this generation passes away, including that.
Which, BTW, as to coming in the clouds of heaven, as it relates to His ascension, and the fact Preterists argue that coming in the clouds of heaven involve judgment, but that God is not physically visible at the time, how does one apply any of that in the same manner to that of what is recorded in Daniel 7:13? No one in heaven actually literally saw Jesus arriving in the clouds of heaven, and that He was not visible at the time, and that He was returning to heaven coming in judgment upon those dwelling in heaven?
As can be seen, coming in the clouds of heaven can apply in different manners, because, obviously, you nor anyone else agrees that Daniel 7:13 is meaning in the same sense you take it to mean in other accounts involving coming in the clouds. Since Jesus could obviously be phyically seen coming in the clouds of heaven in Daniel 7:13, but not by anyone back on earth, but by those dwelling in heaven, the same can be true in Matthew 24:30, that He is visibly seen coming in the clouds of heaven, but this time by those back on earth.
What is the point of being seen coming in the clouds of heaven in power and great glory if no one literally sees this coming, that this coming is invisible to the naked eye? The Greek word for see in Matthew 24:30 is optanomai. You would think He would have used the Greek word eido instead, if the idea in Matthew 24:30 is that the coming is not literally visible to the naked eye. eido typically involves perceiving something rather than literally seeing this same something with the naked eye. optanomai, OTOH, oftentimes involves literally seeing something with the naked eye. Might not be the case every single time that word is used, but most of the time it is, more than it isn't.
Why do you believe that genea should mean a different word in Matthew 24, when in every other context is means contemporaries?
For one, because in the context Jesus said that in, in all 3 accounts, it was end of the age context, not first century context. Context matters. Context helps determine how something should be understood. If Jesus said this generation shall not pass away, till all be fulfilled, and that He said that in context involving the end of this age, how is it an example of using proper hermeneutics by applying what Jesus said, out of context, rather than in context? Of course though, it is apparently debatable, though it shouldn't be, as to whether Jesus said that in the end of age context or in first century context.