Those ads pay for a lot of the web. It doesn't have to be as intrusive as it is, but if there were no ads, lots of websites would simply go away.
Increasing the signal-to-noise ratio of the web like this sounds fantastic.
The way they are implemented today is lunacy. I won't even use the web without a blocker.
If as tracking and targeting disappears tomorrow, not much would have to change, except that some of the money that has been flowing out of traditional advertising like print and TV will flow back. This would make a dent in the “free” online content for sure but it would be worth it. Personally I wouldn’t lose any sleep even if 90% of the ad funded internet including most social media disappeared or became subscription only tomorrow.