Which is why I said it's an ouroboros eating its own tail. The scale it operates at and given that it's also an ad network guarantees that whatever results it finds will favor its own ad network. It doesn't even have to be intentional since all they're doing is optimizing some metrics and running ML algorithms. There is no single person that could be blamed for the deterioration of the results. There is no way around this conflict of interest and they will continue pushing the envelope to increase their own revenue at the expense of useful results for as long as possible.

If a site is hosting ads from the Google ad network and is barely above being spam then Google will prioritize it over other results in order to maintain its quarterly revenue predictions.