This is why there is ever no guarantee in gambling because no matter how long you are in here, or you say you are an expert, you won't win without the factor of luck. Even with poker or sportsbetting where skills is needed. Still, luck factor is in play because if only skills, I would say, a lot of poker players or sportsbettors are already rich and at the top of their games.
That's why skill isn't really that useful in gambling, even in poker and sports betting. But if slots, craps, or roulette are purely based on luck, then in sports betting or poker, you need a little skill to increase your chances of winning, but it's not enough to guarantee easy wins. A gambler can consistently choose the favorite odds in every sports bet, but ultimately, they'll still lose to the bookmaker. I agree with what you said: if skill played a role in gambling, there would certainly be many people who could get rich from gambling. And I think we should ignore the one or two people who do get rich from gambling because they are so small compared to the number of gamblers.