It is harsh to lay the blame only at his door. I think the best thing we could do as fans is to get public commitments from him anyone in such positions about targets, that we had to achieve something by some date like a league title. All we have on him are vague statements on the new ground and the various iterations. If we had got him to say I want to win the league title by this date or do this by that date. That would be something we could hold him accountable for. Since he's weaseled out of all of that stuff, he gets away without anyone actually being able to challenge his record of mediocrity.
He has been a failure in his current position undoubtedly, but will be here for a long time to come.