In my state (Massachusetts), the number of people who call in to the state’s gambling problem hotline doubled after online sports books became legalized. That is, by definition, a negative effect on the public good. The net number of people seeking help for gambling problems increased by 100%.
It’s definitely bad that twice as many people have a gambling problem. However to assess the NET impact you also have to count how much value/fun/whatever the non-problem-gamblers are having, plus whatever tax revenues you get, increased economic activity from more attention on sports, etc.
Personally I think these companies suck. Just need more work to make a strong good faith argument about it.