Until McDavid proves he can dominate in the post-season, it's always going to be a mark against him. No, I don't expect him to drag his team to a Cup (even though Sid/Geno did it with a roster that wasn't all much better) but I do expect him to do something that doesn't have you asking "is that it?". As of right now, he's a regular season performer who doesn't take the next step, when the play speeds up, things gets more physical and time/space is far more limited (ala Dionne, the Sedins, Thornton, Bathgate, Nilsson, Nash, etc.). That can change and quickly but let's not pretend it's not a factor.
Kucherov is one of those guys who always steps up, even if his team doesn't depend on him alone. If you don't want to take anything away from McDavid because you think all his troubles are team-related, fine (though, IMO, you're excusing his current short-comings). But you have to give credit where credit is due and Kucherov is simply a playoff beast.