The club owner will not spend more money to bring in players because previously they have recruited quite expensive players but the players they brought in were beyond expectations. If you look at Amorim's performance in the Premier League then he is one of the worst managers since the Ferguson Era ended because they finished just a few levels above the relegation zone, although the reason is that they focus on the Europa League but the results are also zero.
Amorim accepted Manchester United when the team was very, very down since it was still held by Ten Hag and moreover Amorim did not come to Manchester United since the beginning of the season, but only in the ongoing season so it would not be easy for Amorim to immediately make the slumped team into a team that immediately rose with the players who were there at that time. I will not blame Amorim for Manchester United's current condition because if you look at it as a whole, maybe you will rub your chest over the performance of the Manchester United players. So there is no reason not to recruit new players if we look at Manchester United's current condition which has failed in two different competitions.