You only have to look at Google Search to see how this plays out. Their ads were also clearly separated and distinguished from the organic content, until they weren't.
And now it's become an anti-signal. If I search for a hotel the top N results are for other hotels, and then results for travel agents, and buried somewhere in this sea of uselessness is the result I searched for. The managers at Google have become self interested promotion hunters, and the programmers weak sycophants. It wasn't like this in the early days when I was there, the best ideas won, but then the B player managers were hired and the rot started.
https://searchengineland.com/search-ad-labeling-history-goog...