You'd be surprised at how ineffectual a lot of advertising is.
Billboards should be just wiped out, there isn't any real utility from them, and for the most part they just make things very ugly.
Having giant ads in public spaces is ridiculous.
You really notice it when you go to a place with not much in the way of regulation and they are everywhere.
Around Paris they have giant neon signs on top of residential buildings, which is really odd because they have more awareness of that stuff, it feels very cyberpunk to me, as far as I know they don't even have that in most of the US even where giant road signs exist.
A small icon on the exit sign is fine for practicality.
Paradoxically, there are ways to make digital ads much more efficient but the system is a giant cluster of a mess. It's hard to fathom but many big companies just throw money out the window and hope that it sticks even with 'great reporting' it's a lot of fuzz, and nobody wants to own up to it - the exec at the company, the agency, the ad buyers, and the marketplace, they are in a weird kind of systemic collusion about it all kind of 'pretending'. Of course some entities are very effective about it as well but the amount of 'bad dollars' out there actually makes efficient spending hard.
There are also very bad issues of scale, and a lot of small businesses just can't compete, in an ideal world there would be a 'locality' effect priced in. The 'invisible hand' just doesn't work very well with most kinds of ads.