I'd say he's done well to win 2 trophies. But that's it. He's woefully underperformed in Europe and in the League. I'd go as far as saying every single United Manager (Rangnick not included, technically Caretaker) has done better.
I'd also go as far as saying the only decent section of form he's shown at United was back from Aug 7, 2022 to Mar 1, 2023. That was a run of 41 games where we only lost 6 games and managed 30 wins hence everyone badgering on about how he had an amazing win rate through 2023. He had a great start at United and that ran out at the 7-0 to Liverpool when Rashford officially became broken and our attacking threat disappeared. From that point onwards it's been a disaster.
Edit:
To put it into perspective, first 41 games he managed 30 wins. In the next 83 games he's managed 41 wins. A huge drop off.