IMO social media needs competition but I don't think it will be disrupted by blockchain or decentralization. It will be disrupted by a continued pursuit of competition by doing things like supporting net neutrality. That keeps the playing field level and prevents current big players from becoming further entrenched. Big tech's monopolies are encouraged by lower-level-monopolies owned by Comcast and the other internet media conglomerates. To solve the problems higher in the tree we should get at the roots.