I can't think of anything more profitable at the moment. Although I don't know in depth the income from online casinos.
However, to create an online casino, you need a lot of investment and be willing to pay for advertising and interact in a forum like this.
I don't intend to have an online casino, I'm more interested in having an e-commerce.
One of the factors that makes me believe this is that there is already a whole audience ready to play in casinos, as they are generally people who bet out of addiction, to make money (or even when they lose, they play just to pass the time). In addition to the fact that there are costs for servers, employees, online attendants, programmers and other costs, unlike physical casinos where the costs are for installations, maintenance, energy and employees and security guards...
Do they make more profit than digital banks, CEX exchanges, etc.?
yeah, but that doesn't mean you can just throw 10k at a fullstack dev and expect them to shit the whole website with all its bells and whistles. As with all things, even in cookie0-cutter online casinos (sites with similar interface and shit) it takes an awful amount of time to get this thing done and going, even more worse if you're dealing with a dev team of a few dozen people which is the case for a couple of these reputable casinos on the market.
The real currency you're spending when you create a casino is not just money, it's the time, the effort, and the massive risk knowing the whole industry is stagnated as can be and there can just be a better platform than what you have right now, and you're not going to be able to do anything about it but cry as your regulars become their regulars.
Casinos are profitable when they are, but they harbor tons of risks that a beginner entrepreneur is advised to not go into the gambling industry for their first business venture.