At the end of the day the likes of McTominay, DDG, Sabitzer, even Bruno and non purple patch Dalot, Awb, Wout etc - these are all footballers who need time and space to be able to play cohesive football. Hence when they face a high octane team that doesn’t let them breathe they crumble. Rashford can also fall into that category as I’ve never rated his general play much.
On the other hand you see someone like Martinez and Eriksen and they have the quality to play amidst the madness. Varane and Casmeiro can also do it but both are much more prone to turnovers.
So it’s about constantly adding players who help the quality on the ball go up. I’d say that Eriksen, Martinez, Casemiero, Antony (retention is very good) and as a squad player Malacia did that. This summer should be about the other positions -probably two CMs, a RB and a CF.
Put it this way - if you a goalie who can’t find his team mates, midfielders who can’t build up play and strikers who can’t make it stick and bring others in - you’ll struggle.