Marner is an elite player and has been the best leaf forward more times than any other forwards this year (yes, even Willy). However, the criticisms of his playoff performances are completely warranted; he doesn't have a next gear. I would be ok with him not being a physical player, but he lacks tenacity when things get hard. Mitch is great at reading a play offensively and defensively, but he often doesn't enhance that by bursts of sheer effort which can lead to key turnovers or restarting a broken up offensive play. He has a had handful of games where he showed it, and Keefe and him called it "buzzing" or something to that extent. Like, it's ok to fail, but I want to notice you failing hard and gassed if that happens. He needs to bring that consistently, win or lose, in the playoffs, but I don't think he gets that it's a wall he needs to break though. By the way, I also believe this applies to Mathews.
I don't dislike Mitch Marner; I want him to succeed, naturally. But the point of this whole thing isn't to have really, really good players; it's to win the Stanley Cup. If he can't do it, and his future contract prevents the team from getting a player who can, then how can one justify keeping him?