I think the steelman arg I've found for crypto as a general social media replacement is based on three pillars.
1. Ownership by default. NFTs are kinda a silly example, but since your wallet ("You") own your the token that represent your assets being able to transfer them around with you whenever you go somewhere new is cool.
2. Authentication with your wallet makes things much better. SSO for the whole web.
3. Alignment of incentives for users + service providers. (DAOs, traditional corps, etc.).
So with a concrete example.
In Web2 social network, the social graph is closed off along with all your account info. If you want to move to a different social media website, you have to reenter all your info and re-friend everyone etc. The corporation chose to ban people, and the only way you can in theory get a vote is through owning a share.
In (the ideal) Web3 social network, the social graph is open b/c all your friends are attached to your wallet. If you want to move websites you can take them with you, or even have you be on multiple front ends. Even better you might get tokens to vote for certain proposals in the DAO, for example such as banning people off the site etc.
Decentralization is valuable b/c it allows the above to happen, not because it's valuable in it of itself. Without a decentralized network there wouldn't be enough trust in the network for anyone to use it (long term).
After all blockchains are basically one giant shared database, if someone thought you can modify it, it loses all value (Similar to fiat money in a way ;) )