Amorim was axed by United in January after 14 months in charge.
Maguire said of the Portuguese: “I think Ruben was really good with me. I pretty much played every game under Ruben when I was fit.
“I don't really have much bad to say about Ruben. I really like Ruben, I think he's got great ideas. The ideas just didn't work at Manchester United.
“I do believe he'll go on and have an amazing career, and his next club he'll probably go and win many, many football matches.
“It just didn't click or work and I think us as players have got to take a lot of responsibility for that as well.
“But I think he has led the club in a direction, and I do think he deserves a lot of credit for that, where he's built a good, solid squad and I do believe that he deserves credit for that.”
He added, “I spoke to him when he left. He wished us all the best.
“I'm sure he would have been upset, but I know he's still really, really young and I'm sure he's going to go on to great things in management.”