The Reds have had their worst start to the Premier League since 1992/93, with four points from their first four games, and Scholes – who played at United from 1994 to 2013 – has admitted Amorim's controversial 3-4-3 system might not be working.
Speaking on BBC Radio 5 Live's Monday Night Club, the 50-year-old former footballer said: "I don't think the quality is there.
"Whatever two out of the four or five they have got in [midfield] - Casemiro, Bruno [Fernandes], [Kobbie] Mainoo - whatever combination he seems to try doesn't seem to work."
Scholes added the Old Trafford side's summer transfer window – which saw the club spend £200 million on Matheus Cunha, Bryan Mbeumo and Benjamin Sesko – has not yet bore any fruit, and referenced United's shock loss to League Two's Grimsby Town in the Carabao Cup as proof something had to be done.
He said: "That's a big issue. I thought all summer the absolute priority was a centre midfield player with legs, who can play and can control a game.
"Goalkeeper was [also] a major issue. Did they really need to get to the Grimsby game to realize [Andre] Onana is not good enough?
"If Manchester United were not in the market for Gianluigi Donnarumma when he became available, that is criminal offence.
"The recruitment side went to buy forwards. That did need addressing, but did it need three of them? I'm not sure it did."
United are currently sat in 14th place in the Premier League, having only scored four goals since the season began – two of which being own goals.
Scholes emphasized Amorim needed to change his 3-4-3 system and playing style significantly if the club wanted to see results.
Scholes said of the 40-year-old manager: "He cannot carry on playing this way, he just can't.
"At some point there has to be a moment where he thinks, 'I have to change something because what I am doing now is not working and I am not getting results'. The proof is there."
Scholes – who won 11 Premier League titles and the Champions League twice during his time at United – insisted he liked Amorim, but said his current system "isn’t good enough".
He continued: "I like Amorim, with everything he says, he seems to be a likeable man. But unfortunately results paint a picture.
"At this moment in time it isn't good enough. At this moment in time if results don't improve, performances don't really matter that much. He has to win some games or the pressure is going to come on him massively."
