I'd agree with a lot of this, but given how poorly they play as a team it's almost impossible to even fairly judge individual players. Pogba in a 3 with good coaching and a system is entirely different to Pogba at United (see Juve or France). I suspect on a purely technical level there isn't actually much that separates Stones and Maguire, but the former looks like he is working hard, still learning and still improving where Maguire looks like his best years are behind him. Some of that is down to the player, but some of that is down to manager, coaches, players around them, facilities and everything else.
I think even with the best manager, though, their overall squad is really confusing and unbalanced and haven't really been signed with a coherent plan. They're playing a 4-2-3-1 which is giving up the whole of the midfield, and is a piece of piss to defend against, in order to squeeze Pogba, Ronaldo and Fernandes into the team.