Wes Montgomery was a player who next to nothing about theory. He had great ears, a great memory and worked his tail off to learn how to produce the sounds he was hearing. Pat Metheny and Wynton Marsailis are extremely knowledgable with regards to theory and application of it. They also have great ears and like Wes, both worked hard to get to their level of improvising. But unlike Wes, Metheny and Wynton used theory extensively. Different approaches to get the same result which is to make great music. Not every player needs theory, but most do. I definitely use it and need it. When I hear something I really like, I don't care if the player making those sounds knows the name of whatever chord they are playing. I just care that the music sounds great.