There was an interesting Michael Cox article in The Athletic the other day about how United negated our fullbacks.
I can't share the whole article for obvious reasons, but the gist of the analysis was that United was able to negate our wingbacks by making them choose between pressing their wingbacks or staying back to mark United's forwards. When Robbo did push forward to press Wan-Bissaka one time, we conceded the goal (foul on Origi notwithstanding).
Essentially, the article posited that if you have fast forwards and centre halves that have enough confidence to beat a press, you're going to ask questions of our approach to the game.
The article did also say that this approach meant that United's centre-halves were left to do a lot against our forwards, which they nearly paid for.
As a neophyte to football tactics I couldn't see fault with the analysis, but I'd be keen to hear more learned views.