Of course Amorim don't need to be judged with his performance this season. If we look at sporting Lisbon where he bought the players of his choice, we can clearly see that he did very well there.
To add that Amorin did not make Sporting strong overnight, it was not in the first season that he arrived that he made Sporting strong, in the first season he began to organize the Sporting squad well, he stayed for 4 seasons as Sporting's coach, this allowed him to create a good team and that is what Manchester United needs, they need a long-term coach, someone who organizes the team and stays with the team for many years, something like 8 or 10 years.
There is no where that Sporting will be compared to Manchester United. The only comparison should be that both uses 11 players to play football. Manchester United is superior to Sporting Lisbon. It is possible that a coach does will with Sporting and fails with Manchester United. I am not saying that Amorim has already failed in Manchester United, I am just giving an instance.
Let us just give Amorim the benefit of doubt because he didn't play preseason with boys and he also doesn't also have players of his choice. Let's wait till next season to see his performance