MacKinnon dominating isn't surprising. He's built like a tank, like Ovy. Sid is a really solidly put together guy for a 5'11 player. McKinnon ooks huge compared to Sid in those Tim Horton's commercials in just their polos. Big and skilled will always beat small and skilled.
Smaller/lighter players can perform well in the playoffs. Best of those in that category this playoffs have been Marner, Panarin, Atkinson, and Eberle in terms. Disappointing guys have been Point, Gaudreau, Ehlers.
P. Kane is a playoff performer.
Playoff hockey is different. Especially in round 1. Intensity is jacked up and so is the physicality. Plus, the coaches can zero in on the top players. Can the player adjust. If you are a 1 trick pony, you're likely to get shut down unless you raise your game to another level to combat how you are being defenced.