Your opponent got a better hand than yours, a hand he did nothing to deserve, so it was luck.
His opponent took advantage of his luck by increasing the bet, that was skill.
The cards that come to you, your opponent, or the table that you don't decide are luck.
What you do with your chips and what is generally up to you is skill.
Sometimes we can't even decide what to do with the chips, when we are in the blind or big blind for example, so the game is more balanced, requiring both luck and skill, leaning a little more towards what would be luck, but still It's well balanced, requiring both things to happen.