One of the most important things to remember as we listen to Advent liturgical readings is that none of them was written to be used during Advent.
Unlike Easter, the birth of Jesus wasn't celebrated in the Church until several centuries after the last biblical book was composed. During this time of year, homilists must constantly fight the temptation to make the texts fit Advent. Since this season prepares us for Christmas, our communities expect us to give a meaning to the sacred authors' words that they never intended to convey.
Third-Isaiah, for instance, in the first reading (Is 63: 16-17, 19; 64: 2-7), isn't anticipating Jesus' arrival when he asks God "to rend the heavens and come down!" He's simply pleading with Yahweh to force those Israelites who have recently returned from the Babylonian Exile to do what's necessary to make God present in their lives. Though the prophet's convinced that "we are the clay, Yahweh, and you are the potter," he also knows that people are no longer rousing themselves "to cling to you."
The prophet isn't asking anyone to look hundreds of years down the road for a special coming of God. Third-Isaiah is simply concerned with his own here and now, praying that Yahweh "might meet us doing right, that we were mindful of you in our ways."
Gifts of Spirit
Likewise, Paul, in the second reading (I Cor 1: 3-9), isn't talking about Jesus' birth when he reminds his Corinthian community, "you lack no spiritual gift as you wait for the revelation of our Lord Jesus." Like all early Christians, the Apostle uses the phrase "the day of our Lord Jesus Christ" as another way to speak about Jesus' Second Coming at the end of the world, not His first coming at Bethlehem.
Many of the problems which prompt Paul to write I Corinthians spring from one source: People are using the gifts which the Holy Spirit showers down on various communities and individuals in ways the Holy Spirit never intends. That's why, in this introduction to his letter, he reminds his readers: "You have been richly endowed with every gift of speech and knowledge."
Both Paul and the church in Corinth know that, because they've misdirected their gifts of speech and knowledge, they're in deep trouble. In no way are they ready to face the day of the Lord.
Mark is speaking about the same delayed Second Coming when, about 10 years after Paul's death, he reminds his community of Jesus' words: "Be constantly on the watch! Stay awake! You do not know when the appointed time will come." The evangelist knows that once an expected event doesn't come as quickly as expected, people will stop doing the things that event demands they do.
Jesus' example of "a person traveling abroad" fits Mark's situation perfectly (Mk 13: 33-37). Without telephones or email, no one knows exactly when that person is returning. When the master is traveling, his servants must be constantly alert, "at dusk, at midnight, when the cock crows, or at early dawn." There's always a fear the master will come home "suddenly and catch you asleep." In such situations, one must constantly "be on guard!"
Once we take the three readings out of the Advent context in which we've placed them, it's clear that each author is more concerned with the present than with the future. Even when Paul and Mark speak about things to come, it's only to remind their readers that their present behavior isn't measuring up to what those things demand.
We never change significantly because of what's coming. Such change only happens when we more deeply understand what's already here.