Amorim needs time to get the current Manchester United squad to be prepared for the rest of the season. We shouldn't use the impact that Ruud got to expect same thing from Amorim. The players knew that their position weren't guaranteed with Ruud therefore they played very well to try and get more playing time but under the new permanent manager, after some players get it that they're part of the first team, they won't be overplaying again but to reserve their strength for other games therefore we mightn't be getting the same energy we use to get from them and it can affect the teams performance therefore it depends on how the manager handle the situation.
They have already gotten the time they need to bring the best for the club. Didn't Erik left and all of a sudden the team turn from low budget players to standard players and from the matches they played after then, they have never loss a single match. They should focus on that energy and be there, what they need right now is avoid loss as much as possible and avoid injuries, they can manage like this until January where the market will open for players to move in and out.
Manchester United has loss much and draw a lot of matches they should have win, having 7 matches with draw and loss is something that will have made them stay in the top of the table or atleast stay close to the likes of Brighton and Fulham. They can still do it otherwise their dream of Eufa Leagues next season is gone for good, unless maybe they win FA cup