Luck in poker. Well, it boils down to this fact-- not all hands in poker are made equal. What do I mean?
It is true that over large enough sample it is one's skill at the game that determines results of hands played, rather then anything else.
But it is one thing to have a coin flip all in for example in a CC MTT NLHE freeroll 6 minutes in vs a stack that already took a beating so is 1/3 of yours, then a coin flip all in 8 players remaining 20k guarantee that would make you an overwhelming chip leader that could just cruise to a multi k prize.
Yeah, you win one you lose the other statistically its all correct. But in which scenario does your hand hold and in which it doesn't makes a world of difference for your
bankroll and ability to play.
There are games and hands that can be considered defining for your long term poker experience. Having those 50-50 hold there, rather in a random low importance situations-- is the factor of luck in this game.