Similar to how Privacy Badger works to block trackers based on whether DoNotTrack is respected, Firefox could have an option for a built in system to detect tracking pixels, block them and when a site uses them or uses overly privacy invading fingerprinting as set to user specs of what level to block all ads on the site. Sometimes people want to have ads for sites they like and this kind of feature seems more heavy than the average extension so may work better built in.