Even now with companies like Unilever, we see them threatening to pull from platforms like Youtube entirely because they think its not worth it.
That's completely false. They are threatening to pull from Youtube/Facebook because of the amount of fake news they allow. The Chief Marketing Officer put it this way:
“Unilever will not invest in platforms or environments that do not protect our children or which create division in society, and promote anger or hate,” - https://www.wsj.com/articles/unilever-threatens-to-reduce-ad-spending-on-tech-platforms-that-dont-combat-divisive-content-1518398578
It has nothing to do with the effectiveness of advertising on those platforms.
I doubt selling data is really going to go away, it's simply too useful. Even for the small startup I was working on last year there was data we wanted to buy at some point. There's all kinds of useful demographic information out there and while Facebook usage is dropping it would be hard to attribute that to data collection. Just look at how popular Android and iPhones remain despite their collecting even more sensitive data!
Plus how many people are leaving Steemit when everything we post is completely public? It's exactly what Facebook does except companies don't need to pay for the info we posted!