It’s enforced for the public sector. Which is frankly great in my opinion. Our communication departments have always been the black-sheep of privacy.
Between us, I’m not sure why they are so addicted to various tracking that tells them that absolutely no one clicked on 90% of their content, but they are, and they lack the technical ability to do it themselves without relying on frameworks that steal privacy information.
I believe people have gotten pretty good about auto accepting anything, in no small part due to the 'hey, just wanted to let you know we use cookies, like every other website on the planet!'.
But if people really did overwhelmingly say no, I just see no way for most of the internet to exist. You get overwhelmingly less per click/impression for 'dumb ads,' and news sites have already had to resort to click bait today. It'd pretty much guarantee anything not owned by one of the top 10 would be paywalled in some way.
Sites that rely on tracking to generate targetted ads might not exist. There are still plenty of sites that don't depend on ads, or get sufficient context without tracking. E.g. a car enthusiast forum doesn't exactly need tracking to know it should show car adverts.
I think the internet would stay much the same as it is now. Companies would simply be breaking the law. As a side effect, I think they'd be more willing to do other illegal things too, such as straight up selling your data. They're already breaking the law after all.
It doesn't really matter though because literally nobody it enforcing this part of the GDPR.