Orbert, none of this is against you, per se, but as a general comment, I don't quite accept the "they quit" argument. Maybe it's because I was in a marriage, and I felt a long time that it was my obligation, my DUTY to make it work, and once I got out I realized that literally NOTHING I could have done would have made it work, I'm sensitive to the idea that some of these people shouldn't be penalized - branded, really - for all eternity by the "THEY FUCKING QUIT" label. Why should a guy like Trevor Rabin, a creative, self-sufficient musician, subject himself to the shit-show that was Yes following the Talk record? He had a vocalist that didn't get along with his bandleader, he had a keyboard player that wouldn't/couldn't play what was asked of him (requiring Trevor to essentially play all the keys parts as well) and a band leader that, at the time, was widely understood to be in the thralls of a pretty impressive - even by rock and roll standards - affair with the cocaine.
Steve Howe, I guess it could be said, HASN'T quit, but his output has noticeably suffered. The recent albums are not at all stylistically what could be expected of Yes as a band and Howe as a player, and having seen him live now twice since Anderson left Yes (including once with Asia), one of the truly, all time greats has been phoning it in, in my opinion. Tempos are down, arrangements are simplified, and I've heard more mistakes from him in two shows than I've heard in 30 years of live stuff before.
Creative, artistic musicians should not be obligated to subsume that creativity to some arbitrary standard of "I quit". It's not and never is that simple. (And yes, I fully am aware of the irony of discussing the importance of a band member supposedly "quitting" on a Dream Theater fan forum).