Centralized or Decentralized There Is No Question
puri.sm
puri.sm
Domains are governed by registrars which are clearly "centralized" according to the definitions of the linked article.
Matrix isn’t p2p by default though - although there is a project to address that: https://arewep2pyet.com
Bots are now a fire-hose of LLM nonsense content, and thus the unregulated service failing in a Tragedy of the commons mode becomes a certitude ( https://en.wikipedia.org/wiki/Tragedy_of_the_commons ).
Good luck though, it would be neat if it did work for some reason =)
i.e. those paying for the storage and bandwidth tend to notice the asymmetry rather quickly.
Everyone must get fed at the table in business (lifeboat politics) =)