A few United players come to mind.
Paul McGrath - in the modern game players just can't get away with the stuff he used to get up to when he was at United, and modern medical procedures might have sorted his knees. A fit and firing Paul Mcgrath would rip it up in the modern era in my view. Great on the ball, athletic and a real fighter. He's like a more athletic version of Maguire.
Veron - just a terrible fit when he came to United, and never quite up to the required physical level for our league. But these days the game is way less physical than it was back then, and even mid-table teams shift through multiple formations per game, he'd have no problem being accommodated now. His range of passing was amazing even during his worst spells at United, I think he'd be marvellous sat alongside Matic in a 4-2-3-1, something like that. Veron looking for a pass with Rashford, Martial, Greenwood etc streaking into space ahead of him? Brutal.
Gordon Strachan - Excelled with Leeds & Aberdeen, so its not like he had a poor career. But he was one of those attacking players who never really fit in during an era where even the best teams were rigid and direct by modern standards. Ostensibly an inside right, he would wander round wherever he wanted on the pitch (famously so, in the teacups incident). These days there are loads of players who do what he does - Mata being one example that's close to home - but back then he was someone who was difficult to accomodate.
From other clubs, John Barnes, Peter Beardsley, Chris Waddle and Glenn Hoddle are all players who struck me as suited to the modern game too.
