> the revenue generated per page view decreases
That assumption is worth reconsidering. It may be that fewer ads would just be more expensive to run and would work out similarly revenue-wise in the long run. The value of lots of ads may be diversification and smoothing out revenue, not increasing net.
If every single website on the planet had fewer ads then the new equilibrium might be roughly equivalent revenue, but many websites only have a single banner advertisement. So much of the redistribution of revenue would end up on those websites.
How to unclog a toilet is always going to get SEO optimized spam. However, most topics don’t get that many views.