> If I visit a site for the first time without any ad blocking enabled, and realize it provides no value, how do I reverse my exposure to those ads? How do I claw back whatever data their tracking scripts collected about me?

The exposure you are talking about is a non-issue, particularly given every site you contact has that same information (even without Ads).

If you are concerned about that level of privacy, you should be using https://tails.boum.org or a no logs VPN.