I can relate. I run Synapse for only 2 users, and every update is like a lottery. "Unable to decrypt" most often. Logout 2-3 times, clear cache, then suddenly it works again.
People still use IRC. You can't run your own server and talk to people on other servers without a load of work, you cannot do any kind of encryption, file transfers (images?) are a privacy nightmare if they work at all, web clients need a proxy. Authentication doesn't really exist. Messages disappear if you disconnect and reconnect unless you set up an additional server that will make it seem like you're always connected.
The protocol was written for a different age. If you're going with old-and-proven tech, XMPP is a much better jumping-off point than IRC. Everything that made it simple and easy to use back in the day, makes it hard to use in a modern setting.
You can't build a modern messenger equivalent on IRC. You need a new protocol.
"New" is relative of course, XMPP is 27 years old. Still, XMPP lacks official support for something as basic as "I want to log in on a new device and see the old, encrypted messages that are on my other devices".
IRC itself is a reinvention of `talk` and BBSware. For as long as there will be new use cases, there will be new protocols.
Because people have different use cases and priorities about chat.
Matrix.org and liberachat used to be connected using a bridge, even then the Matrix side didn't implement the requirements of liberal chat fast enough such that the bridge was abondened.
Matrix attitude towards IRC (and bridge implementation) always felt like a trojan horse. Yes, it brought undeniable quality of life improvements over IRC for those who took the bait, but that didn't have to mean making the native IRC experience more miserable for no good reason. Matrix burnt a bunch of bridges with that attitude.
IRC was so easy. :(