Ronaldo is better than Martial.So Martial plays ok in a couple of meaningless friendlies & all of sudden he is a better player than Ronaldo, yeah, right, maybe he should have shown that on the pitch for the past two years.
But you can make a strong argument that as a team we are better with Martial. He actually plays with Rashford and Sancho, for a start, rather than basically for himself.
It is a team game. Individual quality is not the reason we are so rubbish.
Plus of course there is the preseason issue as mentioned already.