Following their dismal 2-0 defeat at Wolves on Boxing Day, United now sit 14th and have one Premier League win in five of their last games. This was the fifth loss in 10 games for new manager Amorim who has not had the impact many would have hoped for since his arrival.
After the game, Maguire made comparisons to former head coach Erik ten Hag who he says is very different to Amorim.
“I think it's really tough for the manager and his team coming in because it's not like he's come in with a similar style to the old manager,” said Maguire.
“They are the opposite in terms of what they demand and what they want, so it's tough for them because they know they want to work with the team on the training pitch and improve things and the defending principles and the set piece principles.
“So it has been a tough month with games but again we don't want to use it as an excuse. This club demands winning and at the moment we're not.
“It's not good enough for us and the fans.”
Maguire also said: “Sometimes, with set-plays, you've got to hold your hands up and say you can't do much about it, but there's others where you've got to look at yourselves and improve on it. I think the Bournemouth one was tough – a great header, a great ball.
“Tonight, it's disappointing to go down to 10 men, not really give them anything, look really solid in the second half, and to concede again (like that), especially the first of the game. Set-plays are so important in football matches and they decide games.
“A lot of the games when they are tight and 50-50 are decided with the first goal. The first goal has been a set-play far too many times against us, and it's disappointing.”
Maguire continued: “How do we resolve it? Work more on the training pitch. I think teams now are maybe targeting our area of set-plays.
“I think it's about hard work, keep the belief and things will change. We have players who can defend the box well. They will change; we've just got to stick together.”
Amorim’s side face Newcastle United on Monday night in a clash that is a must-win before they face league leaders Liverpool and title chasers Arsenal in the new year.