> doesn't make business sense to put a lot of resources into cleaning up ads that pay google nothing

If we lived in a sane world, Google would be held accountable for every scam they advertise. It doesn't matter if you think someone deserved to get scammed for using an ad blocker, because they never would have been scammed if Google didn't choose to put them in danger for the sake of profit.

"But they can't possibly review every ad before publishing" they say. If that's the case, then they should scale down the amount of ads they allow until it reaches a manageable scale (eg every single ad can be reviewed by a human employee). They might make less money, but it's an expectation we have of nearly all industries (eg commercial truck drivers have to follow extra restrictions in addition to regular speed limits)

Yes. "At our scale, we can't possibly do X" is a reason to not scale. It's not a reason to dodge doing X.

If we lived in a sane world, people would simply pay for what they use. Then we could avoid all this confusion, and google would have large (monetary) incentive to protect it's customers.