It's pretty exciting, making a successful career in gambling. If what you mean is to make gambling a basic job to meet the needs of a day-to-day life and hope to live a successful life and have a lot of treasure, I think it's very difficult.
However, if you expect big gains in gambling, like you win the lottery or get other big wins, it's still quite possible. If you have a lot of money, maybe you can make a gambling site. As a gambling site owner, maybe this can be a promising profession.
Taking up gambling as a profession leads to a precarious life as a career in this profession does not bring regular income. If there is no regular income, it will not be possible to support the family, moreover, it is not the regular profit that will come from gambling, but if one day profit will be lost for two days, then there may not be enough money to support the family. So no matter how many chances there are in gambling it will never be possible to build a career in gambling.
A successful career means your income is consistent and there's a financial stability. Obviously, we can't consider gambling or being a gambler a kind of career to be treated as a main source of income. There are professional gamblers out there who are fortunate to profit but it doesn't mean everyone have the same fate. Many gamblers are losing their money and struggling to earn through gambling.
On the other side, casino is a business, so if we're pertaining to the casino owner as a career chances to succeed are high depending on how they operate their platform to attract many gamblers. But it's not going to be easy especially one should have a huge amount as capital to begin with.
You are very right, and I completely agree with you, gambling has and will never be considered as a career, because it's not something one can depend on for constant or consistent and sustainable cash flow. And like you said, there are self acclaimed professional gamblers who seem to be making it, but trust me, good number of those gambler we usually look up to as professionals sure have other sources giving the money like a business or an investment, they are not living off what they make from gambling alone, and I am saying this with all certainty because I have like two guys here in my area who in the eyes of many, are not doing anything but just gambling, and they are living well, but then, one of those guys have 3 different houses he inherited from his dad, with lots of tenants paying him rent every month, the other guy have 4 buses on the road and the driver delivers money to him every day, tell me now, can we really say for sure that any of this guys is living off what they earn from gambling? Of course not.
And on the other hand, If I ever will become a professional gambler, I will aquire enough money and build my own casino, it's better I am playing on my own casino as a professional than playing on random casinos.