The trouble with explaining away Jesus’ words of “this generation” with ideas like “he means the generation that sees these signs” is that it doesn’t help to explain away Jesus’ words regarding the disciples not making it through all the towns of Israel before His coming in judgment, nor His statement regarding some of the disciples remaining alive before His coming judgment. Jesus’ other two statements completely validate and define His intent for the generation statement, making it clear.
Regarding the Olivet discourse, “Let the reader understand” doesn’t need to apply to one who would read Matthew in the future. The most natural application would be the one reading the prophet Daniel’s words, the sacred text that Jesus just mentioned. Furthermore, in a parallel study of the gospels, you’ll see that the “abomination of desolation” coincides with “armies surrounding Jerusalem.” If you look at when the angel tells John Revelation was written, you’ll see that “Five have fallen” and #6 is in charge of the 4th beast – the Roman Empire, which is mixed with potter’s clay – Judea. If you start with Julius, it’s Nero. If you start with Augustus, it’s Galba. And the temple is standing. Revelation was written between AD 54 and AD 68. That’s your maximum window IMHO. I think it makes sense to put the writing before start of the 1260-day Great Tribulation that decimated Jerusalem.
John tells his audience that he is their “partner in tribulation” for a reason. And Jesus’ previous implication to Peter that His will may be that John “tarry until He comes” proved positive.