United's record goalscorer said the club was "broken" on the latest edition of BBC podcast The Wayne Rooney Show, and he goes to games "expecting" them to lose.
Manchester United's 3-1 defeat at Brentford on Saturday meant they have collected 34 points from Amorim's 33 league games in charge and have still to win successive matches.
The club are said to remain supportive of their head coach despite the damaging loss which left them 14th in the Premier League table.
But Rooney added that some current players "don't deserve to wear the shirt", the side "needs a new engine" and supporters are "waiting for the club to crumble".
"I am not seeing anything which is giving me any confidence, there needs to be big changes in my opinion," said the former England striker, who won five league titles during 13 years at Old Trafford.
"Manager, players, whatever that is. Whatever it takes to get Manchester United back."
