Things like this will test how much EU citizens value their privacy. Of course there will be some sites they will not be able to visit but time will show if they are okay with that. These rules are very similar to rules limiting loans. No matter how desperate a person is and how low credit they have, in the US you can't give them a loan for above a certain amount of interest. That could be terrible for a poor person…
Availability of quality free content is not a problem, the content will just be available from other source.
The big problem on the ads-monetized web today is ranking high enough, and the site that don't want to apply GDPR will just have to compete with the site that do have the extra push the EU market give them. On the advertizer side, they make direct money from content accessibility so they will upgrade their tracker so it is GDPR compliant for EU-traffic with no work from the content publisher. That is a non issue, this is just day one of a big change.
Let's also not paint a rosy picture of the web either. GEO blocking is a common daily reality for people outside the US. Any valuable and popular content is locked already, despite being monetized quite directly (see Netflix, Amazon Prime, ...)