Cavani came on at CF about halfway in the second half, playing with a better midfield, and performed worse than Martial had done. And the latter's performance at LWF was much improved from Rashford's. The reality remains, other than movement in the box, Martial is better than Cavani at all other CF attributes. And other than pace and hogging the ball, better than Rashy at LWF.
You point about Anthony's movement, it didn't just happen against West Ham. It has been a theme for most games he's played this season, constantly making well timed runs in behind or beating his marker to come in deep and provide a passing option through the lines, but 8 times out of 10 getting ignored. His movement inside the box has room to improve, but criticisms about his movement as CF during build up, and laziness, have always been myths even if you go back to his performances during LvG era.
Him not taking the initiative on the wing is not true at all. Wherever he is, he more often than not passes the ball forward if there's a teammate in a better position, carries it if there's space to move into and passes it off at the right time with the right weight for the receiver, and will take his man on if he's defended one on one. However if he receives the ball and is surrounded by 2 or 3 players, he often takes the sensible option to lay it off to the side or back if necessary, and then moves to create space.
Rashford is your guy if you're looking for someone who more often than not will attempt dribbling through 3 players, pass when he feels like and ignore those he wants, and still get picked for the next game.
If I rated harshly and gave Martial a 6/10 for the West Ham performance, then Mason gets no more than a 5, Cavani a 4 and Rashford a 3. Given that Martial recently scored a brace and never even saw the pitch the following game, I no longer expect our forwards to be selected based on merit of their performances or goals scored. Ole having been a forward perhaps has other overriding metrics he's using from training or the changing room.