Except that content filtering isn't about the creation of ad-free public spaces, but rather ad-free private spaces. There are (or should be) only two parties to a web request: the client and the server. Neither Apple, nor the State, nor Google, nor anyone else, is legitimately a party to my session.
The reason that I'm free to use an ad blocker is that it's my browser, and I am free to configure it however I want; the server, of course, is free to try to determine whether I'm actually viewing its ads or not, and may refuse to serve my requests if it chooses.
As for micropayments, I love the idea but people in general seem to be extremely resistant to them. For one thing, they definitely don't want unbounded monthly charges. That could be solved by having a set amount of money, divided up by the sites one visits—but the service that does that would be a privacy nightmare.