Harry Maguire is not a good defender. In the past, years ago, Mourinho pointed out weakness of Maguire and he does not want to have Maguire for his defense system. Despite of some good effects he brought to Old Trafford in his first 2 seasons there, now his weakness has been shown clearly.
However, I don't think it is fair for him to forget all good contributions he made in Old Trafford. Last 2 seasons, without Maguire, Manchester United should have more conceded goals. His performance only decreases dramatically after the Euro 2020. I don't know why he lost his performance terribly like this. Anyway I agree with people about his weakness.
You're right, every fan probably shouldn't forget his contribution so far even though Maguire isn't the only player to blame at Manchester United. Maguire is a good player, but a drop in form is common for him because having such a strong defence, Maguire won't be able to do it alone. All players must have the desire to make their team strong on all fronts, so this collaboration is a factor that may have contributed to the decline in his performance so far. This may also happen to other players whose performance is not good.
Tomorrow, Manchester United will meet Brighton. This is a good opportunity to bring West Ham back to 5th position.