Consensus building doesn't work without centralized mass media. People just have to get used to have different groups with different values inside the same country and be ok with that. Decentralized chains of trust will grow, which was the norm before mass media appeared. Either that, or centralization will reassert itself brutally and force a new consensus.
This type of consensus did exist, and could be reached, in the 1770s, long before centralized mass media. The creation of competing "chains of trust", which see an election as legitimate or illegitimate, a virus as dangerous or fabricated, is actually only possible by the manipulation of mass media. And social media very much is mass media. It's just a version in which propaganda is funneled through the mouths of its target audience.