Just as a note - I ran a large web site/forum for 18 years and then another mid-sized for five and I never used any visitor data for anything…although I must admit to having shown some adsense ads on the larger site. Truth is, they never paid very well.
I happened to find the ad model worked for me - due to lower overhead (just me, part time) and also due to “direct to client” ads. Since there was no such thing as an ad network at the time, I contacted manufacturers of said products (high efficiency wood/pellet stoves, etc.) and had them pay yearly fees from $800 to 10K+ for being featured on the site. I never packed any pages with ads so received zero complaints over two decades. The site was profitable (although I never started or ran it for money!) from the first year until I sold it.
The second site was also educational on robotic tech and cameras. Once again I used ads, but in this case they were affiliate. It turned out there were very few vendors of such products, so the readers were going to buy “Brand Y” almost no matter what…but if they bought it after reading my “free” information, I got a cut of it. That did very well also…although again, not intended to make money.
I will note this. The Affiliate model was one of diminishing returns while the “direct client” ad model was not. This is due to the obvious…once a site can make money with Affiliates, 100 sites (or more) will eventually pop up with little or no content but designed just to slice off a piece of that pie. Income from that site was cut in 1/2 three years in a row. It doesn’t take math skills to see that this is not a sustainable model. Still, if the topic had still interested me I would have kept the site even with just “beer money” income.
What amazes me is these well known sites (CNN, etc.) that literally have 100 ads or more (mostly clickbait stuff at the bottom). That is pure desperation as the return per ad has to be incredibly low.
Top down change in those cases could come from ad networks by their limiting of allowable number of ads on each page. But they have little impetus to do so.
Anyway, just some short stories to show that ad-supported situations can work…seems less so as time goes by, tho.