or, of winning a significant, more than 50%, addition to their bankroll, to be more precise
Oh, did I read you right?
It seems that now you no longer claim that it is impossible to consistently win from a casino (provided the latter stays provably fair in the process, of course). It is just that your winnings won't be that great. And most importantly, it requires a totally insane amount of patience and focus, which addictive gamblers simply lack for pretty obvious reasons (because so much patience requires a truly conscious effort on the gambler's part, i.e. not emotion)