At the very least, ads should be banned or require nasty images like tobacco products.
But this submission is about research showing that the legal market isn't just replacing the illegal market. It expands the market and the bad effects.
That is, they're able to track the deposits made to betting sites and other spending. Bets to illegal bookies are obviously not in that dataset. But if the legal gambling had replaced illegal gambling, the money going into legal gambling would appear to be coming from nowhere. Most likely a reduction in cash withdrawals? But that's not the effect they're observing. The money going into gambling is displacing other spending, including spending on +EV investments.
Given there is now evidence that the theory isn't correct, there's probably not much value in talking about it as if there really was a legitimate tradeoff here.