You've left out entirely a major aspect to luck versus skill. Not all gambling or casino games are one in the same. There's a big difference between playing say black jack than there is in playing slot machines. Games like black jack, poker and roulette all take a level of skill and know how and while luck is certainly a factor, skill is also a major player when it comes to being good at these games. So luck wont cover it. However if you're just playing slot machines lets say, than yes, it's 100% luck driven.
Even though people claim that gambling victories are pretty much dependent on luck and chances, I believe it’ll be completely unreasonable to downplay the essence and importance of skills, especially in the games that you mentioned above. In gambling, there are luck based games and there are also skill based games. A game being skill based doesn’t mean that all you need is skills, it means that your skill and experience are the major player in such games and that’s exactly how it is for some luck based games too. Now people claim that they’ve been able to devise a strategy for rolling the dice, not like I believe it but it’s also not completely impossible.