Of course its an opinion - which is also exactly what your post is.
My opinion is that we've treated Maguire disgracefully. I've never seen United fans abandon and turn on one of their own like we did Maguire.
In my opinion, he was made the scapegoat for all of our problems after OGS failed to implement the 'high line, higher press' system in his 2nd season proper. Any CB would have struggled in that chaotic environment, just like Varane and Martinez have this season.
And of the stats...well of course, it's very difficult to take two or more CBs and claim that one is definitively better than another based on stats, so it's always going to come down to opinions - but look at Maguire's record for England. Look at Maguire's record for United. We're statistically significantly better when he plays versus when he does not, over a sample size of more than three seasons.
Regardless, I'm here defending Maguire but I'm not even bothered about arguing exactly how good (or not) he is...my point is solely that those who have written him off, ridiculed him, turned him into a meme and booed him at OT have let themselves down - in my opinion. He's somewhere between a solid PL defender and a very good PL defender - to argue otherwise is just ridiculous, again, in my opinion.