it's not the fault of the Manchester United coach that things are not working at the club at the moment, actually nothing is bound to work at Manchester united until the team is properly fixed and I thing the coach has emphasized that during one of his interviews with press, he also emphasized the absence of the right players in the squad which is one of the reasons the team is underperforming and a possible transformation of the entire squad if not an overhaul, so I see no reasons why anyone should blame Amorim for the poor performance of this Manchester united side for now, he should be given enough time just as the previous coaches.
Sometime the coach also contributes because the success of a club lies in how it is been managed if it is properly managed they it will succeed for sure and look at Chelsea they have sacked how many coaches now and they have been getting it right so if Manchester United want to get it right they must be ready to get a better coach that will be able to give the club a good management and ten was not doing a great job and I actually support is sack because the club was not yielding any profit at all so ot is better he goes to another club to use is strategy but as for Manchester United they deserve another. The coach might be making the right comment of not having sufficient players and if they can make provision for that and the performance does not improve then there is going to be enough problems, and the coach needs serious selection of players so as to make the club perform better.
No club can do well without having a better coach. The 70% success of a club relies on the coach. Even if a club has better players, with no good coach to manage them, they will hardly achieve anything. But even if a club has average players, with a good coach who is tactically sound, the club can reach a successful level.
For example, just look at Aston Villa and Nottingham Forest. Currently, their players are average, but they are performing better than Manchester United or Tottenham, who have better players than them. In fact, a good coach can transform average players into great players who are well recognized. On the other hand, even if the players are good, without a good manager, their performance will surely decline.
As you said, let’s look at Chelsea's performance currently compared to when Pochettino was their manager. It is the same set of players who were there under Pochettino that are still there under Enzo Maresca, but their performances under Enzo Maresca are great.