On a decentralized web, where in many cases the end user will be hosting their own data, apps become views or interfaces to that data.
A social media app would only be a layer on top of a social media protocol. Your images are stored with you. You can manage and withdraw your permissions easily yourself. See metaverse.
There are no platforms mining your data. You are the miner, and you’re the one who would benefit should you hit gold. Not them.
See Solid – How to get people on board, Solid – Social Linked Data