"Better movement" is a bit far fetched. What does off the ball movement mean to you? It can mean defensive movement or offensive movement. Even in terms of offensive play, it can be separated into different types, depending on the type of the player and how it might facilitate him and his teammates.
Let us compare the movement of Rashford and Martial. Rashford is a kind of player who is blessed with very high speed, high acceleration, an average ball control and good work ethic. So, his defensive movement would be pretty good in terms of tracking the opposition runner. His offensive movement would constitute of attacking the space, running behind defenders in order to make full use of his abilities. Yes, he throws in some skills now and then, but it is mainly short and serves to get ahead of the defender, and once he is ahead, he is at full pelt and as direct as possible.
Martial possesses superb acceleration, high top speed( maybe a bit less then Rashford), elite close control and skills on the ball, average work ethic( recently shown significant improvement here). His movements are therefore developed in such a way so as to maximize his strength on the ball and his acceleration, which he uses to draw defenders towards him thus creating spaces for others and using his ball skills and controls to wriggle out of tight situations. So, why would want Martial to make runs like Rashford, considering they are different types of players? Why would Martial need to make more runs behind if he can consistently beat defenders? Also, once he is in the box, you can see him making runs behind because then he has to finish. Consider his goal against Burton Albion. The thoughball that Rashford provided was struck hard, and bar Mata and Martial, I don't think anybody in our squad would have been able to control that ball. Martial's control and carrying of that ball looked so effortless.
Pogba, Matic and Ander are different types of mids. Would you want Pogba to play more like Matic/ Ander instead of playing his natural game? Martial is much more consistent in his game than Rashford, and until Rashford proves his consistency, Martial should be the one starting games and not vice-versa. I Think Jose is also partly at fault for not being able to make use of Anthony's prodigal talents into his plans more frequently.