I've been bothered by the Olivet Discourse for many years, likely because of the influence Dispensationalist Futurism had over my thinking about it. Also, I was raised up in the Church, and was never given any real background for it, so I developed all kinds of false thinking about it.
But over the years I developed a system of interpretation that ignores all the popular views out there, but takes seriously all of the prophetic schools, being willing to separate each school into distinct and separate ideas. I found some truths in Preterism, though I'm not a Preterist. I found some truths in Futurism, and I am a Futurist. But I discarded some of the Dispensationalist elements that made *everything* about the future. And I recognized that some prophecies were historically fulfilled.
And then I began to learn what themes run through the entire Bible consistently, so that I understood biblical language properly. The Abrahamic Covenant and its specific promises became huge to me. Instead of spiritualizing "Israel" into the NT International Church, I found I could only consistently interpret OT prophecies by keeping Israel as literal Israel. So that aspect of Dispensationalism I could accept.
Finally, ignoring all of the popular views out there I took seriously exactly what Paul said, in light of the biblical language and in light of the biblical themes. It was not difficult, then, to understand the Olivet Discourse.
The O.D. was just one more prophetic reference to Israel's fall from grace and ultimate exile. Jesus said that in rejecting him the nation would be cast out of their land until they came back to God in repentance. That is exactly what the Prophets had said to Israel about the approaching Babylonian Captivity.
Luke 21, to answer your question, describes the "Great Tribulation" as a *Jewish Punishment,* and not the Antichristian Tribulation we hear so often. It is a time when Israel is set aside and loses their Kingdom to the Roman Nation, who then takes up the mantel of God's Kingdom. So while the Gospel is spread throughout the Gentile world, Israel languishes in her Diaspora.
This is exactly what Luke said:
Luke 21.20 “When you see Jerusalem being surrounded by armies, you will know that its desolation is near. 21 Then let those who are in Judea flee to the mountains, let those in the city get out, and let those in the country not enter the city. 22 For this is the time of punishment in fulfillment of all that has been written. 23 How dreadful it will be in those days for pregnant women and nursing mothers! There will be great distress in the land and wrath against this people. 24 They will fall by the sword and will be taken as prisoners to all the nations. Jerusalem will be trampled on by the Gentiles until the times of the Gentiles are fulfilled.