His style is the biggest issue in our system
His lack of quality is his main issue. He was already getting exposed in Ole his system multiple times. A system that kept him close to his own goal and had Fred + McT in front of the defense.
He just got exposed less often than in 'modern tactics'. When he can stand in his own box and head balls away he does fine but a tricky attacker can fool him even if he just stays in his own box. He isnt agile enough to deal with tricky or agile attackers and clumsy enough to foul and give away a penalty. Or atleast scare fans into thinking of the possibility that VAR will look at his defensive action.
Maguire is very slow and he isnt smart enough in his positioning to compensate for that. He also isnt great at positioning and too slow to compensate for that. Maguire also keeps the ball for way too long and is also very capable of bringing his teammates in trouble with his passing (pass to Eriksen last night for example). He also likes to lunge into high risk tackles which completly takes him out of play if he misses. Then sometimes there is his lack of concentration which allows situations like Giroud his goal in the World Cup semi final.
What kind of system does a player with those clear weak points in his game work well in? The best you can hope for is exposed less often i think.