Onana has poor debut for Manchester United but again he is only one player in the squad and defense system. Other players must cover Onana better as no goalkeeper can block all shots from opponents.
when Onana and Maguire are played in the squad, it is the best chance for United's opponents to win. Ten Hag had to admit how his current team was very bad. they scored 12 goals, but they conceded 16 times.
I'm sure Ten Hag as a manager knows where his team's weaknesses come from. I don't know what he did to make the fans dissatisfied. on social media, we can see how fans condemn several players, even Ten Hag is not free from fans' blasphemy. they don't just want to see their team win against weak teams. but they want to see how United shows improved play.