It’s a two-sided market and it doesn’t have to be either/or. Google has a wide range of advertisers so it can find one that converts on your site and it has a wide range of sites so it can find ones that work for a given advertisers. Also Google has a large database and user inventory for personalization so it can find ads that convert on your site even if your site wouldn’t attract ads otherwise. the personalization economy has all sorts of ads and might be brand destroying in the case of retargeting but you see that crap everywhere whereas many Google alternatives run brand-destroying ads and pay you $0.00 after rounding.