Oh, well, yeah. That explains it then. The default matrix server isn't good for anything because its bitrate is low, yet everyone makes an account there.

So you have a limited bitrate anf thousands of people to serve. Fluxer is the same. It's just not as bad yet because there aren't as many people there.

If you're approaching Matrix like a centralised service, you're doing it wrong. You must set up a server for you and your friends, and then federate with the rest of Matrix.