[acdha]

Only for the most simplistic implementations. More advanced implementations and incorporating page reputation took care of that pretty well for many years — Google’s quality decline started some time after they merged with Doubleclick in 2008 (notice how they haven’t done much innovative since?), and started allowing abusive sites like Quora or Pinterest to bypass policies against things like search cloaking, presumably due to things like large Ad Words purchases. All of the scam domains I see outranking legitimate results have tons and tons of ad impressions for Google.