Yeah, generally you need time to actually turn over a squad. A competent recruitment team capable of good decision making on the recommendations of scouts and analytics staff usually help achieve that.
Every manager we've had since Ferguson has been setup to fail because of how much responsibility in recruitment has been placed on them. That's not normal at any serious club in football right now and there's a reason for it. Sure, manager important and nice, but depending on them as much as United generally have in deciding on transfer targets is a major error. You need people dedicated to watching, scouting, and evaluating players outside the club to help guide those things, because a manager's primary focus should be molding and developing the squad that he's, you know, managinng.
Happy we agree.
This isn't even to suggest every manager we've had has been great or not at all culpable in their failures at the club, but at some point there's pretty clear consistency in how bad our recruitment has been from evaluation of talent to the actual negotiations on fee and wages. We have asked far too much from our managers whether or not they were the right person for the job.