The supposed Jesus himself(or the writer of the gospel) said that he would return in his generation, not 2k+ years hence. Prophecies were meant for their time and shortly thereafter, not thousands of years in the future. Imagine trying to prophecy events 2 thousands years from now.
A lot of people at first think Jesus meant immediately including his apostles.
That is one reason Jesus gave them the illustration at Luke 19:11-15 about a man that would have to travel far away [heaven] before he would return having received the kingdom of royal government.
-[Psalm 110:1; Dan 7:13,14; 2:44]
Matthew 24; Luke 21 have both a 'minor' fulfillment, and a 'major' fulfillment.
Back in Jesus day the 'abomination' of verse 15 proved to be the political Roman armies in the year 66-70. -Luke 21:20,21.
All the features or events that Jesus described that would be part of a global composite 'sign' -Matt 24:3, did not happen in the year 70. For example: Verse 30 at that time all the tribes of the earth did not mourn.....or such a great tribulation verse 21 that the world had never seen. So it would have to be the generation that would be alive when all the features of Jesus 'sign' would be occurring on a world-wide scale including verse 14 having the kingdom or royal government proclaimed in the hands of Christ as king of God's kingdom government.- Isa 9:7.
'This generation' would be the people of Matthew 25:31,32 that are alive or living on earth at that time of Jesus 'glory'. Since the 'abomination' in 70 was political, then at the future time leading up to Matt 25 the 'abomination' would also be political. In the past, God used the military ax, even on his own people if they corrupted themselves. Today we see on a global scale that the world's religions, or world's religious sector, has run afoul playing false to God and his Word. The political world sees a dangerous religious climate brewing in the world today such as religious terrorism. With backing the United Nations can be strengthened to turn on such troublesome religion and with God backing the political 'kings' or world powers will turn on the world's composite false religious 'queen' or religious sector. -Rev 17:2,17; 18:7,8.