I don't think FLoC provides a default - that's the browser's job. We can all guess what Chrome's default will be (although I'd also expect that Incognito will disable or at least reset FLoC), but regulations like GDPR/CCPA might still require affirmative consent.
Re: obnoxiously bad service, frankly I think sites should run however they want as long as they are truly transparent about it (not just a buried EULA). I prefer open sites, but nobody should be forced into service just because I have an IP.