During that WJC, McDavid was fairly small, Eichel was solidly built for his age and against playing above his age group. Now? McDavid has gained strength which was shown at the last World Juniors. But when McDavid burns Eichel's ass, the WJC tournament didn't count. Ok bud.
I haven't watched every game, Eichel made some really good plays in the Ottawa game, Toronto game wasn't quite "generational." I rely on some information from posts from people who did watch games, I saw one of McDavid's game and I'll be seeing the rest of his games in the pre-season as well. He could have had a hat-trick according to Ryan Rishaug, but regardless he had a generational game against Phoenix.
When they were facing teams like Finland, Slovakia, Germany, those teams didn't really have a "shut down" line. The players are sort of equal, it's like asking should Keith-Weber or Vlasic-Doughty play against Ovechkin. They are great players at their level regardless and should do a good job shutting them down.