His main technical issue is his first touch, can struggle when the ball is bouncing off the turf. 2 consequences of that, he can get planted when getting ready for a touch, making him a pressing target and at times he is not aggressive in dropping for the ball because of uncertainty in that area.
He has a decent passing range, outside of Pogba he strikes that right to left switch as well as anyone in the squad, but his lack of left foot can make him predictable and he can overthink passes instead of just hitting them early, can cause interceptions.
That ability is very overrated when you lack vision and execution. We usually see him do that 4 times, only being successful twice in 15 games or stomething, in situations where it's just leading to nothing. Rooney was 10 times better at it and only sometimes it was a handful skill swapping up the play, unless he hit one behind the defence, which McTominay frankly pretty much never did. so it's pointless talking about him having a decent passing range when it's got no use.
Compare him to Fred who might not be able to hit the ball that hard and switch the play so elegantly (he more often does with a different technique over a shorter range) But the ability to be available for the ball, in tight spaces, little pockets to play 3 times more passes per game in the build up, quickly speeding up the play with one touch is just in different space compared to Scott.
This is much more important and people just don't realize that at all, often people who never played football, and don't see the big picture and are vowed by non-effective stuff in football.