Your friend is looking at it on a hand-to-hand basis where there is a certain amount of luck. But the luck only go's as far as what cards are dealt. There is so much more to it, though. There are the things such as reading your opponents, betting patterns, odds, pot odds, ect. that don't involve luck.

There is another aspect that is much more broad than each hand - money management. If you have game play skills(what I mentioned above, for example), money management will allow you to make your losses smaller and your wins larger.

If you judge it hand by hand, then, yes, it might be mostly luck if your not a very good player. But when you judge it from the long run, the luck factor dwindles down significantly.