Not just this, but he was probably in our top 3 players of the
season in 4 of the last 5 years.
I understand people saying that selling him wasn't the problem, it was not replacing him. But that exposes some basic naiveté to me. In football, one in the hand is definitely worth two in a bush. If you've got someone who is off the right character, exceptional fitness, no trouble under 4 different managers, don't get rid of him because you 'might' have found somebody better.
The reality of these things is that you end up with someone like Amrabat. He might theoretically be "a better, footballer" but there's a good chance he's not, so why take the risk when you've got a proven solid pro with a good reputation amongst his peers and can deliver solid performances most of the time? Even if you throw in the occasional shocker, it's still better to keep someone like that than get rid (imho).
I'm not saying people think of Amrabat like this, but I do think people massively underrate squad cohesion, tactical diligence, and even 'likeability' in a footballer. Even after fecking Paul Pogba and Jadon Sancho, heck even people like mhki and Kagawa. Being a good five a side player or a "streets will never forget" baller is almost the last thing that makes a good professional premier league footballer. It's not romantic to say so, but United would have done better with 2 Freds, 2 James Milners, and 2 Ward-Prouses than an infinite number of Anthonys or Martials