Scholes said "I wouldn't be happy either" playing Mourinho's pragmatic brand of football, in comments that threaten to reignite his feud with the Portuguese manager.
The former England midfielder pointed to a gulf in class and playing styles – with Pep Guardiola's free-flowing Manchester City, who won the title 19 points ahead of their neighbours last season.
United begin their campaign against Leicester City on Friday, after a downbeat pre-season when they lost 4-1 to Liverpool and Mourinho voiced his frustration over a lack of new signings.
"It doesn't really look like the players enjoy... playing the way they do," Scholes told AFP in Hong Kong, where he was promoting 433 Token, a blockchain-based system aimed at nurturing young talent.
"If I was there playing... in that style of play, I wouldn't be happy either," said Scholes, who won 11 titles and two European cups at United under Alex Ferguson.
"As a manager, you want your team to entertain... That very, very rarely happens at United these days."
The latest salvo from the TV analyst follows a highly publicised run-in with Mourinho last season, when the Portuguese thundered: "If Paul one day decides to be a manager, I wish that he can be 25 percent as successful as myself."
Scholes said the former Chelsea, Real Madrid and Inter Milan boss, whose sour demeanour in recent weeks has triggered speculation over his future, now finds himself in a "difficult position".
"If his team don't do well, if they're not playing well, they're not entertaining people, not challenging for the league, then he possibly could go, yeah," Scholes told reporters.
"But he's got great experience, he's been at top clubs. He's been in difficult positions before. He's in a difficult position now, I think, but he needs to try and find a way out of it."
He added: "It just doesn't look like United are in the right place at the minute to challenge for the league."
Scholes also urged French World Cup-winner Paul Pogba, who has been linked with a move to Barcelona and is said to have a difficult relationship with Mourinho, to stay put.
"What his relationship with Mourinho is like, I don't know from the outside. The one thing that does surprise me is Barcelona: I don't see him as a Barcelona player," said Scholes.
"He's (got) a different style to them. But Paul's a really talented player. I want him to stay at United."
Scholes is not the only one from United's famous "Class of 92" to have questioned Mourinho's management. Ryan Giggs and Gary Neville have also been less than enthusiastic in their assessment.
And Scholes said United may have missed a trick in not appointing Giggs, now manager of Wales, when Ferguson retired in 2013, pointing to Barcelona and Real Madrid's shrewd gambles on Guardiola and Zinedine Zidane.
"We don't seem to be brave enough in England to do that. I think United had a great chance to do that with Ryan Giggs. They didn't take it," he said.
"For some reason, they wanted to go down the safe route. And you'd have to say, was that the right thing to do? You're five years down the line, not really.
"Okay, they've won the Europa League, they've won the League Cup (both in 2017). But look, they're not the trophies United want. They need the big ones.
"So you'd have to say taking a risk with someone like Ryan or somebody else, a young up-and-coming manager would've been a safer bet."AFP