I'm not sure about the latter part, but I think the first part is pretty clearly true.
The theoretical economic value of advertising is new product discovery. If you needed a thing but didn't know there was a solution and you saw an ad, then some of the value you gain would be attributable to the ad.
Imagine a world entirely without ads. Would you really be lacking a lot? I doubt it. Especially with the internet, it's easy enough search, to receive word of mouth, to read reviews, or to ask friends for help with a problem. But let's assume it happens some. Ads might at least get you to a solution sooner, so count the value gain there as well.
Now subtract all the money spent on things where ads encouraged a purchase that was not valuable or even wasteful (e.g., didn't live up to expectations, was fine but the need wasn't urgent so it sits in a closet, was bad enough that it actively cost you extra money). Subtract further the amount of money spent on ads, hundreds of billions of dollars per year. Subtract also all the time spent watching, listening to, and reading ads. Further subtract the amount of value that would have been gained had that time been used as a person wanted. And further subtract all the value that could have been gained had those creative people creating ads been doing something beneficial.
I can't come up with any reasonable numbers that suggest advertising is a net societal positive. It exists not because its targets want it, but because businesses are in an arms race to manipulate consumers in ways favorable to the advertisers. It's like military spending: most of it happens not because anybody really wants it, but because nobody wants to lose to the other guy.