I can't think of anything more profitable at the moment. Although I don't know in depth the income from online casinos.
It may look like a profitable business but there are downsides like large investment for a bankroll, fierce competition, risk involved in being hacked, data protection requirements and all that.
You're looking at a business by comparing margins and see that casinos earn a lot so they must make a lot, but they have to constantly advertise, pay celebrities to endorse, hire streamers.
I think that making a successful shitcoin that people will kill themselves for like they did with NFTs 3 years ago is much more profitable.
Do they make more profit than digital banks, CEX exchanges, etc.?
Depends on what casino you'll compare to what exchange. IMO the average crypto casino earns less than coinbase or binance because they made millions from listing fees.