I think Barna's research is quite compelling.  I also believe its "all of the above", and not so simplistic as people might imagine.  I think millenials are enigmatic and I'm pretty confident that, after working with teens, twenty's and thirty's for the last 3 decades, young people are particularly searching for authentic "connection", vertically and horizontally.  I think liberals and conservatives both tend to focus on peripheral/secondary issues.  "The main thing is to keep the main thing the main thing", and I think the main thing is the longing for deep intimate connection with the Godhead, and to be loved unconditionally by people.   Isaiah 61 also manifests the burning desire in every heart to see people experience freedom on a personal and individual level, as well as the transformation of society that includes social justice issues.  Thanks for stimulating an important conversation.