Luck is certainly a part of the game. Without luck, losing players / fish - there would be no possibility of "professional" players who consistently rack up win numbers. With that in mind - the fact the game has "pro" players - that means it is a skill based game. Those who cannot grasp this concept or further themselves beyond their current level of understanding is what hold them back from being a winning player.
I am not the best but I like my skill level and insight into the game. What I have learned over the course of only 5 or 6 years has certainly helped me play the game better and to understand what to do more in tough spots. When I am playing the game there is a reason for almost everything I do. IE: when I check call, when I lead the turn - when i check call flop and turn and lead the river, and so on and so on. The point is - today rather than just the basic game principle or instinct to call or raise or whatever the action you are taking - now my actions have logic behind them. Knowing my opponents tendencies - the board texture vs their range - what is a bad turn card for their perceived range, etc...it all plays into my decisions now and as a result when I implement my strategy - I win more pots than I used to.
The other side of things is by knowing when my opponent could have missed a draw, is giving the sense they are trying to push off a strong hand - and so on - sometimes making what could be the correct call will cost you $$. It goes both ways but overall the more you know and understand the better decisions you will make.
In summary my knowledge of the game had led me to better decision making and winning more pots / games then I used to and while i may not be the winning-est player to ever sit at a poker table - i have certainly improved over the course of time and will continue to do so as long as I can