How you do that is part of the lifecycle of an Ad platform. The ephemeral "quality of ad" is completely subjective and will forever be inadequately measured (to anyone's satisfaction for very long). Eventually all ad networks are subject to market pressures in pursuit of margins. Third party ads eventually arise from the existing technical implementation of ads (tons of untrusted code running in js and vpaid applications), even when "prohibited". There's nothing special about Amazon's platform. Lots of platforms have been the "new hot thing" with "total control".