Your post supposes a lot of things that there's no proof for. You say Maguire's confidence is shot because basically his own fans are on him, so does that mean you think Harry is on here somewhere reading comments about himself? It's not fans - rival fans or our own fans - who are giving him abuse that is unsettling him, it's legitimate, reasoned criticism from professional pundits and football writers. Yes, fans on here and elsewhere love to bandwagon, but I'd argue there as many pro-Maguire blinkered fans as there are anti-Maguire blinkered fans. I've read on different forums that Maguire is in the top 3 CBs in the world and that he's equal to VanDyck. Some people actually believe that, but I see no evidence in favor of that argument and hours of evidence against it.
I'd also like to put to bed this notion that somehow when Maguire is in his beast mode he's a titan compared to Lindelof - it just isn't true. Lindelof has always played a certain style as a defender, and it's not the English way of using your head as a battering ram, which is, not coincidentally, one of the things Maguire fans like about Maguire. It works in the England set up because the England team is static. We will likely disagree on England's performance at the Euros and at the Russian World Cup. I saw England being timid and compact and conservative. Shaw's goal against Italy was the only expansive moment in that game. Southgate favors the safety-first method, and it not only isn't that fun to watch, it also loses to a team that decides to play with a little flair and panache. Maguire looks better in the England team because everyone around him is also playing the same way. United does not (and should not) play that way. Lindelof plays more like a continental CB.
People did indeed blame Maguire's mistakes on Lindelof and came up with reasons why Maguire had to cover for Lindelof's deficiencies, nobly sacrificing the purity of his own game to help the team. It's just not true. And we are seeing evidence of this with Lindelof and Varane together. Sometimes people say it's DeGea not patrolling the box that explains why Maguire can't defend, others say it's the weak shield ahead of him in McFred that doesn't give him enough protection, and others say it's poor, scared Lindelof who is afraid to muss his hair by heading the ball. The recurring theme is that it's anyone and everyone but Maguire. Take Maguire out, put Lindelof in, and we are better. I don't agree that Maguire is better than Lindelof - although if you somehow got Lindelof to play in the England team he would look worse than Maguire.