Our entire attack has spent year after year being designed to be more about individual brilliance rather than teamplay and quick interplay. One thing that was extremely obvious last season and to a slightly lesser extent this season is that when Sancho gets the ball we won't have any other player near him to actually combine with. He's just completely isolated and expected to make something happen. An in form Rashford can make those situations work with his blinding pace, but Sancho relies more on having players to combine with. It doesn't mean it doesn't happen at all, but certainly not enough to really take advantage of Sancho's ability.
Martial has always been the one exception which is why our entire attack always seems to go up a couple of levels whenever he's been fit and in form. He brings everyone else into the game, and always had great interplay with Rashford and Pogba in particular (Bruno too if I remember correctly). If he actually manages to stay fit I think we'll see both Sancho and Antony benefiting massively (and Rashford might actually go up another level again).