They've made some excellent signings like Bruno Fernandes, who has been their best player since signing from Sporting Lisbon in January.
The jury is still out on players like Harry Maguire and Donny van de Beek, who cost £80million and £40million respectively.
While the signings of Alexis Sanchez and Memphis Depay turned out to be disasters and there are certainly more that could be added to the list.
It is not for the want of trying, though, with the Man United hierarchy often setting their sights high but failing to get deals over the line.
Here, talkSPORT.com looks at the players the Red Devils have nearly signed over the past decade but ultimately failed.
Erling Haaland
In January, Haaland was the most coveted talent in world football after smashing in 28 goals in 22 games for Red Bull Salzburg.
His modest buyout clause of just £18million made him a target of some of the top teams in Europe.
In the end it came down to two options: Manchester United or Borussia Dortmund.
United were unwilling to meet the terms set out by his agent Mino Raiola, which included a buyout clause of around £68million.
He ended up joining Dortmund and hit the ground running in the Germany with 33 goals in his first 32 games.
Jadon Sancho
The will he/won't he Sancho storyline over the summer kept everyone's attention.
United were very keen on signing the Borussia Dortmund star but were unwilling to meet the £100m+ price tag set by the Bundesliga side.
Sancho is arguably one of the brightest young talents in world football and would have been a great addition to Ole Gunnar Solskjaer's side.
Bids were reportedly made, deadlines were set and missed and nothing eventually happened.
Watch this space, though, as it could still possibly happen in the future.
Gareth Bale
Bale left Tottenham for the bright lights of the Bernabeu in 2013 and went on to be a Real Madrid superstar winning four Champions League titles.
His career has gone full circle and he is back at Spurs, albeit on loan, but things could have worked out very differently.
David Moyes wanted Bale and Man United as his first signing and he came close to an Old Trafford move.
"I wanted him to be my first signing at Manchester United," he told eirSport.
"We came close, spoke to him, but he had his heart set on Real Madrid and we couldn't talk him out of it.
"It was a real disappointment because I saw him as a Manchester United type player."
Moyes went on to make just one major signing in his first transfer window… Marouane Fellani from his former club Everton.
The Red Devils were also interested in him this summer before he joined his old club back on loan.
Manuel Neuer
Edwin van der Sar announced his United retirement in 2011 and he was eventually replaced by David De Gea but the Spaniard was not Sir Alex Ferguson's first choice.
Fergie was very keen on Manuel Neuer, who was at Schalke at the time.
"Eric Steele (United's then goalkeeper coach) had been scouting David de Gea for quite a while, but then Neuer came on the scene at Schalke. And I think Schalke would've been happy if we'd have gone and taken him," recalled Sir Alex.
"So my problem was Eric, because he was adamant that we must take De Gea. I said 'but Eric, the boy Neuer is the complete unit; he's mature, his physique is unbelievable', and he says 'yeah, but in three years' time, De Gea will be better'.
"Eric and I went out to watch [De Gea] against Valencia away, and the things he'd been speaking about - his agility, his confidence, his speed - were evident.
"And Eric had been building a relationship with his parents, and was so adamant, that I had to trust him - and I'm glad I did, because he was right."
De Gea has been a good servant at Manchester United but Neuer was arguably the best goalkeeper in the world during much of the last decade.
Who knows what could have happened if they had gone for the German instead.
Raphael Varane
Ferguson was inches away from completing a deal for a then 18-year-old Varane back in 2011 - only for Zinedine Zidane to snatch him away at the final hour.
"I hurtled down on the train from Euston to Lille to sign the young French defender Raphael Varane," Ferguson wrote in Leading in 2015.
"David Gill was getting into the finer points of the contract with Lens when Zinedine Zidane got wind of this and somehow scooped him up for Real Madrid from under our noses."
United then ended up signing Blackburn defender Phil Jones, who is firmly out of the first-team fixture at Old Trafford and looks likely to depart the club in the near future.
Thiago Alcantara
Thiago won seven Bundesliga titles with Bayern following his arrival from Barcelona in 2013 but he was linked with a move to Man United that nearly went ahead.
The midfielder shone at the 2011 Under-21 European Championship and Sir Alex Ferguson was desperate to sign the creative talent. Xavi, Andres Iniesta and Sergio Busqeuts all ensured the youngster was not playing regularly at Camp Nou at the time.
When Fergie departed in 2013, Thiago was once again high on the club's wishlist and now readily available for transfer.
Yet the bizarre reason the transfer never happened could haunt United for years.
According to ESPN, new boss David Moyes was desperate for a marquee signing at Old Trafford and was linked with the likes of Cesc Fabregas and Gareth Bale.
But Ferguson had reportedly agreed a deal for the then-22-year-old Thiago after being made aware of his desire to leave the Nou Camp in search of first-team football.
But the plug was pulled on the £17m deal for Thiago, despite talks being at an advanced stage.
Moyes allegedly said he did not know enough about the player, who was already a Barcelona first-team regular and who made his full Spain debut two years prior.
Toni Kroos
After lifting the World Cup with Germany in 2014, Kroos was all set to swap Bayern Munich for Manchester United but the deal collapsed.
Moyes was sacked as United manager meaning he swapped Germany for Spain and signed for Real Madrid.
Speaking to GQ via lifePR, the Madrid man confirmed that a deal to move to Manchester was agreed following preliminary talks.
"I knew before that Manchester wanted me," Kroos said. "And Moyes underlined that absolutely. It was a really nice afternoon with very nice people. We talked a lot about United's footballing plan which convinced me.
Kroos added: "I am not somebody who worries about contingencies. Yes, it was close. I almost went to Manchester United. But it did not happen that way.
"One thing I can say for sure: Manchester United would not have won the Champions League three times," said the 33-year-old. "Manchester United is not a club you go to for a short while. Manchester United is too big for a year or two. This is not a club to end your career.
"Since both the player and the club must have a clear idea - I signed with Real Madrid until 2023."
N'Golo Kante
Kante helped Leicester lift the Premier League title in the 2015/16 season and was a standout star along with Jamie Vardy and Riyad Mahrez.
The midfielder looked likely to leave that summer and eventually joined Chelsea - helping them to win the title the next season.
But Manchester United boss Jose Mourinho was very keen and he tried to convince the France star to move to Old Trafford.
"It was amazing to have Mourinho call me, even though I'd been warned before how he would appeal to me," Kante said.
"I listened to his arguments about why I should move to United.
"But at the time I was hesitant between staying at Leicester or leaving for Chelsea.
"My discussions with them were well underway. But when I spoke, I had a good feeling with Conte."
Sadio Mane
Mane has been a consistent star in Liverpool's much vaunted front three that has seen them claim Premier League and Champions League trophies.
He joined the Reds from Southampton in 2016 but, unsurprisingly, other clubs were also interested - one of those were Man United.
"I was really, really close because I even met up with them," Mane told the The Mirror.
"So I was coming, I was there and I spoke with the boss who was there before [Van Gaal].
"They made an offer, but in the same week, Klopp called me.
"He said: 'I think it's the right club. The right coach for you, and I think it's better that you go to Liverpool'.
"For me I think it was the right time as well. I said, 'I am going to Liverpool'."
Robert Lewandowksi
Lewandowski has been a top striker in the world for a number of years now and shows no sign of decline.
2020 has been a standout year for the Poland international, helping Bayern Munich win a treble, and would have been a shoe-in for the Ballon d'Or before the award was scrapped for this year.
Back in 2012, United were very keen on signing him from Borussia Dortmund.
"I was speaking with him [Ferguson] after two years at Dortmund and at that time I was really thinking about a move to Manchester United," Lewandowski told the Guardian.
"Because of Ferguson and because of Manchester United.
"Borussia Dortmund said: 'No, that's that.' That was the first time I was thinking about the move because if you get a phone call from Sir Alex Ferguson, for a young player it was something amazing. That was a special day for me."
Manchester United's business in the transfer market has been hit and miss at best over the last few years.