Yes, online casinos do actually payout. Legal online casino apps and sites take the extra steps to ensure that all the available games are tested and audited for fairness so that every player stands an equal chance of winning.
Winning from online casinos requires expertise. It also requires being smart. By checking out different casinos before choosing one, censoring your losses and wins, getting all available bonuses, and playing free games before a real game, you can improve your chances of winning.