You're arguing against your own logic. You're saying it's stupid to blame the GK because we have conceded so many goals, highlighting our inability to cope with defensive transitions, stating how poorly coached we are (both of which I agree with) and THEN blaming Maguire. The problem was Solskjaer. Simple as that. It was all tactical.
However, I do think De Gea's impact has been massively overstated this year. He has been OK and made one or two good saves but the rest you would expect him to make. In the words of Roy Keane...'that's his job' He has already made big errors in conceding two goals against Atalanta, the Silva goal against City, at least one of the goals against Watford, and that's just off the top of my head. To not even be at Christmas and think our GK has conceded at least four bad goals is not great when shot-stopping is the only thing his proponents claim he is good at.
The statistics back up the view his impact has been hugely overstated.
His xGA vs the actual GA is basically 0, so that's neither a negative nor a positive contribution (purely based on shot-stopping). He has faced the 6th-least shots in the league, yet conceded the 2nd-most goals and his 'percentage saved' is bang in the middle of the pack in 9th.
It's not a black and white either/or.
The primary problem is the coaching. But within that individuals can still make their own mistakes. If De Gea fumbles a shot into his goal, he obviously has to take a large part of the responsibility for that goal. Just as if Maguire, AWB or Shaw make unprompted errors, they take responsibility too. And this season we've conceded quite a few goals where individual errors have been made, which is obviously more likely to happen when you're badly coached as players are under more pressure and put into worse situations. So when I'm talking about the things that aren't De Gea's fault, it's fair to point to both the coaching and other people's individual mistakes. It's not like I'm saying Maguire or AWB are more at fault than the coaching either.
And in this particular season, with quite a few members of our back 5 in poor form, De Gea doesn't have to be particularly outstanding to be one of the best performers from that bunch. But that doesn't mean he
hasn't been one of the best performers from that bunch either.
Relative to the rest of the team, he's having a decent season. That doesn't mean he isn't an issue generally but it does make it strange to name him as one of the main culprits for the problems we've faced. He might be
an issue but off the top of my head there are managers, coaches, midfielders, right-backs and centre-backs as much or much more to blame
this season.