I think the problem (at least when we're discussing a new managerial appointment on this board) is that people expect us to sign a manager who'd guarantee a Top4 spot. Unfortunately, that was Mourinho and that didn't happen.
What we need to do is decide (broadly) what kind of team we want to be, sign the players who fit in that general philosophy and look for coaches who fit the bill. When Klopp signed for Dortmund, his record at Mainz read 105w 78d and 83l. It's very good for a club of that size, but when you look strictly a the numbers, there were probably better candidates for the job.
At some point, you have to make a decision and stick to it. It's not rocket science. Achieving greatness takes time and you need a lot of things going your way: a good scouting network, people working together in harmony (DoF+manager) and a couple of lucky breaks in important games. What tinkles me off is that it's more or less what Levy promised in his infamous 'DNA' letter. Six months later, we haven't reached step one. We couldn't even find a manager who fit in with our philosophy. And that's after spending three months looking for 'Mr Right'.
If you know where you're going, it doesn't matter if you make the wrong appointment because the next guy will carry on and, hopefully, benefit from his predecessor's work. Right now, we're just banging our head against a wall in the hope of finding our way to a good place. It's absolutely ridiculous. You have to wonder how they make their decision. Again, it's not rocket science.