It's not that easy, I can't remember which player explained it, maybe it was Pires. Martial on the left come inside, he moves towards the weaker side of most defenders, they have to either defend with their weaker foot or make awkward movements in order to reach with their stronger foot. On the right it's the opposite, if he goes outside he is on the stronger foot and natural side of defenders, when he comes inside he is on his own weaker foot and goes toward his weaker side, it's not the same approach, not the same game. Ronaldo isn't as good on the right than he is on the left, same thing with Messi, they have to tweak their game significantly in order to make it work. You have players like Perisic, Reus, Coman or even Mbappé that manage to do it but they have good left feet and it comes naturally to them, the vast majority of players struggle a lot when you change their side.