Miles Davis on Steve Miller: “Steve Miller didn’t have his shit going for him, so I’m pissed because I got to open for this non-playing motherfucker just because he had one or two sorry-ass records out. So I would come late and he would have to go on first and then when we got there, we smoked the motherfucking place, and everybody dug it.” http://www.openculture.com/2015/05/miles-davis-opens-for-nei...
Life isn't and shouldn't be "everyone is fake except this one true artist here." They're all artists. If Miller could magically become a better musician he would have. He probably felt tremendously upstaged by Young's and Davis' talents. I'm sure hearing this broke his heart.
Miller himself got his early breaks through concerts backed by Chuck Berry in 1960's. I can't imagine him calling Chuck a low talent nobody, even though by then his music was very much out of style as blues-based and psychedelic guitar rock took over. Everyone has to ride someone else's coattails to make it in this industry. No need to be an asshole about it.