Answer:
When I speak to young adults about why they have left the Church, they often say something about the homily. The preaching is boring. It's unrelatable. It's long. It's like listening to insider baseball. It's like a terrible essay with no organizational structure.
While one would hope that our young adults would stick around, recognizing that the reality at the heart of the Mass is worth receiving even when the preaching is mediocre, perhaps these young adults are testifying to something important.
Some young adults may be looking for entertainment in the homily. References to the latest music or films. Practical advice.
But there is something about the dissatisfaction with preaching that suggests young adults know that the homily is meant to lead to an encounter with Christ. It is not an occasion for the priest to offer a seminar in historical-critical exegesis.
It is not time to offer one's disconnected thoughts on a papal encylical or apostolic exhortation or general cultural phenomenon.
It is not the time for the priest to regale the assembly about the recent vacation or stories from seminary.
The homily is a form of liturgical speech that is meant to facilitate an encounter with Christ at the heart of the Scriptures.
As I've written elsewhere:
...the homilist's developing capacity to attend to the fullness of the human experience, as manifested in the local assembly, is more than an effective rhetorical strategy. Such attention to human experience must necessarily occur in liturgical preaching in which the Christian is invited to offer the entirety of one's life to the Father as a gift of love...the liturgical homilist should become an expert in the human condition, aware of the subtle desires that are fertile ground for the enfleshment of the Word in our lives" (Liturgy and the New Evangelization, 66).
If homilists want to speak to Millennials, they don't need to pepper their preaching with references to Taylor Swift. They don't need to turn preaching into a twenty-five minute stand-up comedy act. Rather, in the homily, they are to use human speech as a way to facilitate an encounter with Christ. To prepare us for the offering of our lives at the heart of the Eucharist.
The problem here isn't with the Millennials. It's with preaching that has forgotten how to proclaim the Good News of God's transformation of the world.