After hearing my 2nd ever rousing rendition of the Messe de Tournai, a 13th century mass for three voices, I was talking with one of the singers about how much has changed in the way modern musicians regard those early styles of polyphony.
My theory as to why the practice has become so much more lively: The singers who are putting vitality into the art are not the top earners. Since they don't make a lot of money they need some compensation for their effort, and that must be their joy and satisfaction when, refusing to be bored, they find the life in the line.
It reminded me of a performance I heard recently which was so tedious that I could hardly stay politely seated next to the friend who had invited me. The next day, as I wondered how those players could tolerate being so bored I realized it had to do with their being very well paid, indeed. Inevitably the prestige that goes with their conspicuous positions breeds confusion in the audience. How will they recognize boredom when they hear it, if they 1) have paid so much for their tickets and 2) the players are all reputed to be "top notch."
Go and hear young people. Patronize the less-than-famous. Take a chance on the unknown. Let yourself be, perhaps, surprised.