But every graph can be shown nicely and things which are common sense don't need a metric to proof it.
Part of the problem is that they're fighting against financial incentives that they themselves created. There's plenty of upside and little downside to abusing it, so it's just endless whack-a-mole.
Another issue is just how bureaucratic the process has become. They want it to look good to the regulators and the courts, so they put up with a pattern of abuse for five years, then announce some well-reasoned but narrow policy change (e.g. "product reviews now need to be actual hands-on reviews"), and... a month later, spammers are just adding an extra lie on all the fake review websites.
Looks like people don't acknowledge that # of clicks is no more important metric. That seemed to be important when it was the only meaningful performance metric. But the ultimate metric that matters to money is advertiser budget allocation. If they see Google search performs worse in terms of conversions, they will cut their budget there. And this is the real problem that Google has.