Of course, if you play roulette or dice, it all depends on luck. But if you play poker or bet on sporting events, then a lot will depend on your skill. And the higher your skill, the more likely you are to win.
Even your are right that if a person have good skill on analysis of sports and as well you also mention games like poker may be they are winning probability can be increased but if you look at the ultimate result then it is also depends on luck.
Like no matter how much you skill on your Sports analysis you can also lose bet like we see on many matches that is stronger team lose against a weak team. And also in poker it is also depend on what types of card you are getting.