Unbelief, ignorance, lack of love, and the fear of man are all barriers to the life of the Kingdom, but I believe the #1 barrier is lack of commitment. I don't believe so-called "Millennials" shy away from commitment - just look at Extreme Sports athletes today. I believe that the Church however has "misread" them and has sadly offered a "watered-down" version of the Gospel, that essentially is a perversion of the Biblical one.