As a casual student of poker, with a small library, I understand that both skill and luck are part of the game. However, we need to be careful on how we define "luck" in the game. The place most players blame luck is on the river, when an opponent "get's lucky" and catches their card to win. Yes, we can call it luck, but it is actually "probability". That player had a small chance of getting the card or two needed to win - and they did. Lucky for them.
Skill comes into play when knowing whether or not to bet, call, raise, and by how much to ensure that over the long-term, you are winning those hands where the opponent is losing those lucky draws.