Earlier quoted context omitted.
Exactly. We need a standardized method for meta tags that accommodates arbitrary user (or rather service operator) defined categories. We also need a broad push to force all websites to adopt said tags so that parental controls can work effectively. Government enforcement of particular categories is one option there (but not the only one, browsers could just start refusing to load any site that doesn't send the tag).
I think you'll find that trying to neatly bin the internet into neatly defined categories is something of a fool's errand. I guess the canonical example is centuries old fine art that shows a bit of nipple. what about whitelists? this never comes up anymore. I can load profiles from the 'child safety council' if that's what I want, and should expect to cover some of the overhead in evaluating all the submitted links.…
In practice I don't think it's an issue. What I'm arguing for is the infra to facilitate self categorization and (likely) also a legal requirement limited to only a few specific categories. For example the government might mandate that porn, social media, and user generated content all be accurately tagged and provide legal definitions.
Nothing about what I describe would preclude additional layers of categorization such as (but not limited to) whitelists. In fact it should improve such efforts by providing a standardized method they can use for arbitrarily fine grained categorization that will be compatible with other software out of the box.
Note that my tagging proposition could be applied per network request. So if the service operator wants to it should facilitate filtering out (for example) a comment section without blocking access to the rest of the site.