The existing tech he's referring to is what we're approaching with the web as it is now (silos of centralized systems, in which information could be controlled)

The existing tech he's referring to is what we're approaching with the web as it is now (silos of centralized systems, in which information could be controlled), and the irony is that a large part of why decentralized systems (and tim's construction) are notable is to avoid such a scenario. They explicitly do not solve the problem of fake news, because they explicitly do not want to live in the world where fake news is a solved problem (because the issues that go with its solution are far worse than the problem of fake news). The problem is that it is possible to do, and the solution to it is not something we want in general, but we're heading towards it anyways, and TBL is trying to avoid that with his machinations, and the commenter is effectively asking "how does this solve a problem that would naturally be solved with a solution we really, really don't want, and TBL is going out of his way not to solve?".