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.
Word of mouth works for someone with an already established customer base but I can’t even imagine how I could have gotten my business going when I started a year ago without ads. That’s how 99% of my customers found out about me. This is physical flyers though - I don’t do online advertising except for maintaining a some kind of social media presence for my business.