I always find those criticism hilarious. Glass with his "sold out" style made more innovation in WCM tradition than pretty much anyone else in 20th century who lived before him, except perhaps Schoenberg who came close to his levels of iconoclasm. Once you're that good and creative, "you sold out" stops being a valid criticism. Bach would poop out a cantata weekly for the church he was a Kapellmeister at, because his job was to write music for the church for people to listen to during various ceremonies. That's not selling out, that's just working for money.