Objectively speaking, Harry Maguire is not a bad player and he has proved himself to be capable of playing against Europe's best in international competition. With that being said, I am doubtful that he will ever be the right centreback for where we aspire to be.
On the basis of this season, his performances have been largely awful to average. I don't recall him having a particular great standout game for us. We all know that while he is aerially dominant (at least in defensive situations), he isn't very good at 1 v 1s or making recoveries. Put him up against an agile striker and he struggles. At times, he lunges into hopeless challenges which leaves the rest of our defence high and dry. He's effectively a worse version of Smalling defensively, but with better long passing.
The bad thing is that Maguire is our captain, seems to have a substantial ego, a complete lack of situational awareness and lack of emotional intelligence, which is typified by this kind of statement after a horrible season and his ear cupping celebration against scoring against Albania (he then proceeded to be sent off against the mighty Watford the week after). I believe the reason why the managers keep on picking him is because of the lack of any viable alternatives and the captaincy which surely must factor into the decision. Instead of taking the criticism on board and trying to improve, I get the sense that Maguire is just waving it aside and continuing to believe he's a great defender when he isn't at this moment.
Yes, two managers have continued picking him. But look how he has repaid them. In fact, his daft and completely unnecessarily red card at Watford effectively ended Ole's stint as our manager. If you are going to make this kind of statement, don't go on and ship 4 goals against our most hated rivals.