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.
Wow, even if we imagine some different situation where information about a new development, service or creation is needed, that’s what reviews and journalism are supposed to cover, not advertisement. (In b4: the observation that those have tragically been becoming more and more indistinguishable from advertising.)