By advocacy and persuasion and some level of agreement through democracy.
>By that standard, we're done
Laws can change, so we're never done.
Society is a never-ending churn of social forces. There will always be a matrix of people who are good and bad and indifferent, who think similar and different to one another. It will never settle.
To answer your question about sports gambling in particular (though you did not ask me): I think the bets on specific things happening in a game are more manipulable and thus damaging to sports in general, as well as to the addictive properties of gambling, than simply betting on an outcome of a game.
So yeah, some aspects of gambling are bad enough that, now that we've seen the impact it's having, we should consider some more guardrails.
Even the college kid libertarian I used to be would say that the government should enforce "an informed consumer": That people should know what mechanisms gambling companies use to entice and addict people.
[edited for tone]