Manchester United's manager doesn't have a magic wand to make a team play well when many other managers have come and changed them. Now all the current manager is doing is just waiting for the Premier League to finish, it doesn't matter if the team finishes in 8th to 16th position because in those positions they don't have access to European competitions
but Manchester United still has the Europa League which is a great competition, so all the focus now should be on the Europa League and then when the transfer market opens, they will sign new and good players. It takes time to build a good team.
This can't be an excuse, they can't play so badly in the Premier League just because Amorim decided that they can win the Europa League and thus save the season. Remember ten Hag, who bragged about winning a trophy for the club every season, but it didn't help him even taking into account the fact that Manchester United were much better in the Premier League. What is happening to the team now is just a disaster, and in my opinion, even winning the Europa League will not save them, because what's the point if with such a team they will be obvious outsiders in the Champions League.