maybe the ads should be relevant to the content
Back in the old days, that used to be how it worked... but soon ad networks learned that showing ads "relevant to the user" had better click-through rates than showing ads "relevant to the content", with the content becoming only a data point to classify the user for the best ads that might sway them.
Soon after, advertisers caught on the trend, started blindly paying for ads targeted at user profiles, then ad networks stopped showing stats about whether content-targeted or user-targeted ads were getting better conversion rates, and everyone has been coasting on blind faith in "the algorithm" ever since.