I think it would have been confusing to the people Jesus was speaking to if he meant a future generation, rather than THEIR OWN PERSONAL generation.
He explicitly used the pronoun YOU when talking to them. They would have understood this as such.
The apsotles also would have found it confusing if Jesus had a far-future generation in mind, after telling them dozens of times, YOU... & THIS generation.
Also to keep in consideration, the context in Matthew 23. Jesus is speaking TO the scribes & Pharisees, saying "Woe unto YOU...."
The things that Jesus said would take place in THEIR lifetime / genration WERE FULFILLED... just as he said they would be.
Yes, the same types of people have lived before their generation & still do to this day. But the prophecies were directed TO them & that's who Jesus was speaking directly to.
Everything from Mat 24:1 - 24:34 HAVE been fulfilled. If you notice, Jesus does change the perspective in verse 35; And in verse 36, he describes "the last day... & his second coming".... He makes a transition in context.....
Mat 24:35 Heaven and earth will pass away, but My words will by no means pass away.
Mat 24:36 But of that day and hour no one knows, not even the angels of heaven, but My Father only.
This event, the "second coming", is still yet to be fulfilled.
That hasn't happend yet. I agree with that.
But not EVERYTHING in Matthew 23 & 24 is about the second coming & last day.
Know what I mean?