The idea feels like sci-fi because you’re so used to it, imagining ads gone feels like asking to outlaw gravity. But humanity had been free of current forms of advertising for 99.9% of its existence. Word-of-mouth and community networks worked just fine. First-party websites and online communities would now improve on that.
The traditional argument pro-advertising—that it provides consumers with necessary information—hasn’t been valid for decades.
Online stores would be the exact wrong place imho. Take amazon, it become a outdated and rotten because of advertising changing the ranking and fake reviews and endless duplicates of items. There is also a lack of advancement for filtering. You’d want more trustworthy reviews, information, measurements and also more community functions to help find what you really need. Advertising would run counter to all of that.