I always say throughout these years, Manchester United failed to have a good attack and defence line.
Since you were talking about Hojlund, let's remember how pissed Cristiano Ronaldo was in his position with the team, he had to leave his old club, United of course where he was a hero there, and find another club to start good. Hojlund isn't any lucky than CR7, he failed and will continue most likely. He has to get out and restart elsewhere. It is as simple as that. Many players find their perfect balance in other teams like Osimhen, Lukaku...
Cristiano Ronaldo played well for Manchester United but they perhaps created pressure and forced him to leave by seeing his playing style does not contribute too good things for the team in general. It can be a good assessment on Cristiano Ronaldo's contribution for their club but they failed to replace Cristiano Ronaldo. Seasons later, they still did not find any good striker who can score goals regularly for them like Cristiano.
This made their decision and bad treatment on Cristiano Ronaldo are like a massive failure and their club are still in a big crisis, not only at a striker position, but the other positions. Ruben Amorim will face with a lot of tasks and pressure to do well in a new season with his mission of rescuing Manchester United.