It is de facto centralized around Matrix.org & the servers they run, which was originally funded by Israeli Intelligence so who knows what they are doing with all the metadata flowing to a single cluster of servers. Also using the eventual consistency model like a blockchain duplicating all data between all nodes while resilient is incredibly wasteful on storage & RAM. The costs are so high, most medium-sized servers with open sign-ups needed to shutdown due to storage costs & scaling up a node costing too many extra resource for CPU/RAM. There also wasn’t anything lacking about the prior arts—but open source & startup like to reinvent more things than they should.

Ejabberd, which I mentioned, can run nodes with 2 million simultaneous connections per node & run on meager hardware in comparison with an extra decade of stability / battle testing.