He has those winner traits like you mention, the correct mentality and application on and off the pitch. He has football IQ and technique so it's a shame that he lacks the physical traits (height, pace). Good to see his form pick up recently, especially his quality on the ball and ability to break lines with his passing.
He lacks height indeed, yet not entirely pace. He ain't the fastest dude around, he is not a snail either, he has his acceleration and speed in him, even with the ball at his feet. In this last aspect he went into space with the ball at his feet a few times leaving some players behind, he has to do it more thougth.
Luke was mentioned sometimes here, yes he is faster, really fast, but many forget that he received the Trent/Walker treatment when being a left back because of gifting his back time and again and no pace will help you if most of times you gift that space and the team itself itsn't tight enough between its lines.
More than pace, for any defender in this system, this team needs "partners" all over the pitch. If the backs aren't there or need help, the DM/pivot inmediatly must get his arse into our area yet he more than probably be tired running like the energizer rabbit because we have no real control of the mid many times.
If there is a dead ball situation, our forwards must learn how to get their man and at least bother, if we advance from the back, our lines must be close, not with huge gaps, if the rival moves the ball from the back, they must be press. With United rivals arrive to our backline almost fresh not few times, they don't go throught a mine field like any team with this system (or any system for the matter) must create in order to defend better as a team. As extraordinary any Baresi, Maldini or any traditional Italian or even defensive alike Argie side, you have to go throught Stalingrad to face the back four, you'll arrive there without a limb.
United needs better understanding between players, between lines, be tighter. You'll always face some ocasion where you'll get exposed with three backline, no matter having Bolt in the back three.
His height bothers more in dead ball situations, there is his worse drawback regarding his physique but like any team, the bigger dudes and specialists are the one that has to take task of going after such situations and more than going to the ball, going to the man targeted, not loosing him.
That is the usual issue in United and with a keeper in Onana that doesn't want, nor like to command his area, that it's a BIG ISSUE.
Also sometimes the nitpicking with every player it's kind of over the top, at some point the rival will win those balls, it's also the ability of the rivals what makes them connect and score, there is no team even with the taller dudes that always wins in his area, or at crosses so it has become a bit silly at times.
Anyway till United does not solve its issue between lines, find the 11 usual suspects creating couples all over the pitch, till we don't score more (that gives confidence, that doesn't make every ball the last one), till the ball doesn't go forwrad and comes back faster than a tennis practice front, our mids, defenders, we'll have to deal with too many edgy situations that at some point will make them comitt some silly mistake. Even because of being tired, or caught out of position because of some pinball situation where United hadn't even try to control the ball properly to find a better path to attack or simply hold it, manage the tempo, reset.