I agree. I really liked Quin. I thought he was doing a great job building up the players he was given until the expectations skyrocketed and games of high importance hit him straight in the mouth and his two best players decided it's better to settle scores off the floor than to work together for the common goal. Now part of his job is to deal with that and still steer the ship in the right direction so he must bear some of the responsibility too.
With that said, I think a lot of people are massively underestimating Quin's offensive coaching. Donovan Mitchell - fallen off Mike Conley - Royce O'Neale - Bojan - Rudy is not the starting lineup of a team you would suspect is the best offense in the league two years in a row. But his(and the FO's) overreliance on Rudy as a defensive anchor ultimately doomed this team as a serious playoff contender. They just refused even to attempt diversifying our defensive schemes even after the current one was unequivocally destroyed in the playoffs, only for us to see it again this year... the exact same thing.
Overall I'm not as negative on Snyder and not as cheerful about his departure as many here, but I absolutely understand why both the Jazz and Snyder might want to try something different.