I didn't hear much negative response from musicians. But the classical world had its doubts. There are some musicians who think improvisation is the real way to explore music. Others say, sink your roots into one plot and find different meanings in different ways. It's a risk.
Most people are afraid of it.
It's like opening a door to a dark room and going in. You don't know what you'll find. But I find that fascinating. You walk into a ring of light, start to sing, and something happens all of a sudden. You find a part you want the audience to do.