I'm not suggesting making radical changes. I'm suggesting Maguire should not be in our best 11.
Personally I think with the players we've got, I agree with Southgate in the fact, 5 at the back, with wingbacks, is our best approach as our CB's aren't the best we've ever had (far far cry from the days of Terry/Ferdinand etc), therefore, for us to stay as defensively solid as possible, 3 CB's is probably the best approach with 2 sitting/defensively minded CM's in front....sometimes depends on the opposition too mind.
However, just having the system isn't enough, you need the players and at the moment, we have at least 3 better CB's available than Maguire, based on form/stats (whatever you want) in the last 12 months.
Just because he had a decent World Cup & Euro's in the last 4 years should not justify the reasoning in keeping him in the first 11 when his club form (past 12/18 months?) (and more recent country form) has been shambolic.