The two types of systems you’re discussing now are orthogonal.
On the one hand we have the web-of-trust systems originally discussed. On the other there’s age-gating and verifiable credentials, which is increasingly a state-imposed requirement that platforms and hosters need to decide for themselves whether to comply with in order to continue operating in a given jurisdiction.
Self shouldn’t be compared to trustnets. The point of Self and attpslabs is to be a more transparent alternative to the egregiously data-harvesting alternatives in use by the incumbents. That discussion can be kept to the Private Age Assurance for ATP topic.