Martial is finished at United. His issue was never talent. He's always had that in spades. Martial's problem is mentality and his inability to withstand the pressure. We've clearly seen that, because anytime he was indisputed first choice, he would thrive. Then, when he faced compeition for the shirt, he wilted. After 6 years at the most pressurised and scrutinised football club on the planet, I think we can safely conclude he isn't cut out for it at Old Trafford.
So Martial is simply not a big club player. He's a small club player with pretentions for the big stage. Like Ben Foster. He'll do well elsewhere where there's less attention on him.
DvB is a different case. He seems to have some decent fundamentals. But every minute of PL football he plays he looks like a deer in the headlights. The guy has some very visible deficiencies to his game. But I have no idea where they come from or how easily they'll be solved.
It could honestly go either way for Van De Beek Everton. But there is some possibility for him to still make it here.