I think our defence is often unfairly slated. Our wingers are neither pressing enough from the front, nor coming back to prevent the overlap.
I think it's not that the front 4 do not press, it is more that they do not press effectively enough. I mean, Rashford, Bruno, Matrial, and Greenwood will all try to cover a man in the general zonal position afforded to them in a 4-2-3-1 but it's better for them to press more tactically to push the ball out to a player who isn't comfortable on the ball and then attack more. RBL (of previous seasons since I haven't watched them much this season), for example, force the ball out to the opposition fullbacks and then cut off all avenues of a pass and press with more intensity at that point with a goal of winning the ball back. In short, there is more purpose and a clear tactic behind what they do there. Our front line will press but we have no real cohesive game plan apart from attack the ball carrier and hold positions to press zonally.
I think it's understandable that they do not drop back to help defend overlapping fullbacks. They are inverted forwards after all and are simply better suited to playing further up the pitch. I think they do drop deep at times to help out - but not consistently enough to make me think there is a tactical instruction involved for them to do so in all defensive phases - only ones where we are sitting deeper and positioned behind the ball.
At the end of the day, this is not something the players have to solve - it is in the hands of the manager and the coaching staff and what they want our players to do. From what I can see, the players are playing to instructions for most part with a few lapses here and there when caught out of position.