I get what you're saying, but you need to look at the context. Was he given the necessary tools to succeed? Do we think he is a good HC, if given the right tools? The right tools meaning a good OC and a backup QB.
I think this team is a backup QB, a good OC and a few players (kicker??) away from being a very good team. The D is near elite, the ST's have been great since Wild returned, the main issues are on offense, and some rookie coaching decisions that O'Shea will hopefully figure out with his experience.
I'm on the fence with O'Shea but I'm leaning towards keeping him one more year.