You can turn on filtering and subscribe to a whitelist today. People don't seem to be satisfied with that solution. Why not? The answer to that question is what needs to be solved.

There's no web standard for labeling content, so "subscribe to a whitelist" today means crappy page or network-level content blocks implemented by a third party tool that has no understanding of the actual content on the page or application. That's not at all what's being proposed in this thread.

With a universal labeling standard the UX would be much better, and there'd be a much greater incentive for website owners to participate (they'd be implementing a universal standard, not adding support for one particular parental control tool).