You basically answer your own question here. Many of these guys were merely inadequate for the role or roles given to them, but some had a far larger blast radius than the others--I'm looking at you, Mr. Wannstedt. He took over a team with a hall of fame defense and chose Jay Fiedler to be the QB. We wasted drafts and draft picks due to poor talent evaluation, and when we could have had a top 10 QB he was unreachable for the whole gosh darn day. So, consequently, we did not get Hasselbeck and we did not get led by Hasselbeck to the Superbowl... we stuck with Fiedler.
We had an elite defense. At times we had an explosive running game. All we needed was a guy like Hasselbeck.
The runner up is Joe Philbin. The team didn't really become clownish until his antiques arrived. They drafted Ryan Tannehill. They cuffed Ryan Tannehill. Philbin's locker room festered with Tannehill hate. There never seemed to be any unity with the front office. It was just an awful string of years to follow this team. Love or hate Ryan Tannehill, he made careers for Hartline and Bess and gave Wallace his best season ever, and in return they assassinated his character once off the team. Thugs will be thugs, and that was the Joe Philbin locker room atmosphere. Can't forget the rest of the clown show that went on with the other guys I've selectively chosen to forget the names for.
To be honest with you, I added Sparano there, but I felt bad after that. He really was Wanny part two except he didn't **** up the team, and inherited a built team. As for Philbin I agree.