In fact, it would be the right decision, another thing is that it is simply impossible for financial reasons. United (like probably any other club) cannot afford to change the team entirely when changing the coach. Therefore, United are expecting targeted changes that will gradually lead to the team that Amorim wants. As for selling/renting players, I don't think there are many options. Who needs Rashford with his salary? PSG were after him before Ten Hag.
Amorim needs a serious strategy to drive the club forward. What Manchester united is facing now is multidimensional, for instance, Manchester United has an issue with their squad composition. While there's an overload of attacking players, there's equally an issue with a limited defensive which was an issue underlayed by the past administration of Eric Ten Hag, now Amorim needs to fix that in the midst of a limited resources available to him. They must also work on their recruitment process and strategy which is something I believe Amorim have to address in the interim.
Amorim's tenure is working on a formation that'll strengthen the team's forward line. And the player he's eyeing to do that job is Gyokeres. But the problem is that PSG seem to have an eye on the player. He has scored 22 goals in 18 matches, including a hat trick against man City on November 5. His performance can be duplicated in Man U to help lift up the club's position in the EPL.