The Red Devils boss has faced criticism from former Old Trafford greats such as Paul Scholes but knows harsh words are to be expected because of the club's struggles since he took charge last year.
Asked about the criticism of ex-players, Amorim said: "I think it's normal.
"It's a fact that me as a manager of Manchester United, I think we are underachieving. We should have more points, especially this season. So, I take that naturally.
"Sometimes they don't have all the information and see Manchester United with the standards they lived here, always winning. It's hard for them to see their club in this situation."
Amorim rejects the notion that the attacks make his job more challenging, suggesting that it is results that determine how easy he has it in the dugout.
The Portuguese coach said ahead of Monday's (15.12.25) Premier League clash with Bournemouth: "Not winning is the issue.
"The problem is that me as a manager, I'm not doing good enough. That is a fact also and I can accept that. The only problem for them is that Manchester United is not winning and is not in the position that it's supposed to be.
"If you are winning, there is no issue."
United's promising midfielder Kobbie Mainoo is believed to want to leave the club on loan in January due to a lack of game time under Amorim and the coach has stressed that he wants his players to be "happy".
He said: "I will be really pleased if Kobbie comes to talk to me about that. I just want my players happy.
"I understand every individual has their goals and the frustration doesn't help anybody.
"I'm not going to say what I would say but I would talk to him.
"I am completely open, that is clear. I have my ideas and that is also clear. I will not change if I don't believe it but I'm open to speak with any player. I love that."