The goalkeeper is not the only problem but it's definitely a great problem in Manchester United. They don't have strong defenders to protect the team and the whole team is not in a good situation to have better results but the fact about the goalkeeper in Manchester United is mostly about changing the goalkeeper while they don't need to. De Gea had a good performance and he could have played for more years in Manchester United but they hired Onana and now this goalkeeper is injured while he didn't even have a good performance when he was playing for Manchester United.
Actually, previously I have said several times here that everyone doesn't have to blame Onana but let's look at Manchester United's defense and that is the problem point that Manchester United has at the moment, the defense is a little weak and for Onana I think that his performance is quite good and we remember How did Onana contribute to saving Manchester United's goal in the Champions League match at that time and that was Onana's actual performance.
Erik Ten Hag's task is actually not that difficult, just bring in quality defenders to strengthen the defense line and I still want to see Manchester United shine again like before.