Jesus is speaking to the cynical members of the crowds, the type who have been holding him and John to different standards and finding fault with them both. On the one hand, John is too ascetic. On the other, Jesus is too much of a bon vivant in their sanctimonious eyes. (Don't you love it that when God came to earth, he was accused of having too much fun?) And Jesus basically tells them, "If I played the flute, you wouldn't dance; If I sang a dirge, you wouldn't cry: You'd stay distant and 'objective,' but without the wisdom that would give your life flavor."
When God plays the flute for us, he wants us to get into the music--to dance. When he sings a mournful song, he is offering us communion with his grief. The flute and the dirge can both express divine wisdom.
I've been hearing the dirge lately, event though we've been singing Christmas joy. A sister I am very close to has been diagnosed with cancer (though we don't yet know what stage it is). So today's Gospel resonates. "There is an appointed time for everything." For all I know, my friend's diagnosis could be the announcement of a new mission in her life, and the doctors and nurses who will care for her a new flock for her to shepherd even as they work to restore her well-being. God may well be playing the flute in a mysterious key.
Maybe that's why the opening words of today's Eucharistic Prayer struck me so much that I am using my rosary beads to pray them over and over: "Father, we acknowledge your greatness; all your actions show your wisdom and love."