I believe that Amorim is a coach with high taste of quality players and it does not mean that the player must be a superstar. The management is desperate to see a new Manchester United full of strength and zealous to win trophies. United performance has been poor for so long and it doesn't tell good about them because they have lost their respect.
You are right, it's not compulsory that Ruben Amorim must sign superstars or already made players before Manchester United's performance can stabilize. If Ruben Amorim can have the eye to sign players that are dedicated to playing for Manchester United, I think Manchester United can start winning their matches in the Premier League even though they don't win the Premier League title. Manchester United's problem can't be solved in one season; Ruben Amorim's target should be how to stabilize Manchester United's performance next season.
If I were the manager of Manchester United I wouldn’t be so much interested in signing big names rather I will shift concentration to scouting players in and around the EPL and championship just as United are doing now with the likes of Cunha and Mbuemo. I think Manchester United are on the right track with this signings they are making lately.