I'm not entirely sure that's true. It's equivalent to asking a platform to moderate all "harmful content" off the site. "Scam" is fundamentally subjective, just as "harm" is.
The real solution is to reform the justice system such that a citizen feeling they've been defrauded has a quick and easy process to get satisfaction for themselves and other similarly harmed people. We need a streamlined, totally online court that excels at gathering and interpreting data, and a decision in days not years. The ad networks are themselves the natural allies of such a reform, but such a change can and should start small as a pilot program at the state level. If successful, it removes the considerable legal-cost moat protecting scammers, and so it no longer makes sense to even attempt such a business, and the world becomes a slightly better place.