In my opinion, professional gamblers or professional players are those people who study gambling a lot and start to see gambling as a source of income. They spend a lot of time studying the games and have good bankroll management. Also, in most cases, these guys write books, have telegram channels and give courses. Now, whether or not they have long-term profits, I honestly don't know. They probably also have a lot of losses, which is why they create paid telegram channels to give courses.
To be honest, I am really surprised by some of the posts above and your post that the thought about the gambling as a profession or that it is possible to book long-term profits with the help of gambling skills is being viewed very positively.
I actually disagree with all these things because I believe in my heart that gambling depends only on luck even analysis skills help sometimes but there also need luck to win. And where the results depend on luck, it can never be taken as a profession for one's own income source, and even if it were taken, I don't think anyone would live a healthy life.
Responsible gambling never views gambling as a profession, meaning that you can be a professional here. Don't get me wrong, I'm not discouraging gambling, but I'm just saying that people should always be mindful of their potential to lose when gambling so that they don't make the wrong decisions.