There is also the conflation that there is some lost potential when advertising can actually sway you into buying something - but the secret is, if you do not already have the necessary economic pressure upon yourself to seek out goods and services in your interest already, that advertising is actually detrimental because it subverts your internal alignment of values through conditioning causing you to make purchases against your base intentions.
The only aspect of advertising of worth is learning products exist, but I would quite easily argue that - especially in the age of social media - word of mouth informance about goods and services that can benefit your life are much more valuable and reasonable and much less detrimental to personal economics than advertising.
How many people bought smartphones because of a TV ad vs their peers telling and showing them how useful they are?
Since we are getting on this topic, I imagine in the case of the downfall of advertising - however that may happen - people would become sociable again amongst each other about what products are good and useful and which have quality. A thousand years ago you would not have known of the quality of rice from a country away but you would know who is the best and worst blacksmith in town and where to get the best ale. We could easily have that again, enhanced with technology to make it a truly global information market.
The private finance of product placement to cause emotional purchases rather than rational ones, by comparison, is dramatically more inefficient.
So maybe some form of advertising is useful, but it would look totally different if what drove it was consumer benefit and not producer benefit.