I and many people i know dont like discord either.
To suggest a more modern alternative than irc we could use matrix, which is an open protocol with working opensource clients such as riot and others.
It has all the modern stuff you need backlogging, synchronization, filesharing, voice and video chat.
The riot client works in browsers, on android and desktop computers.
The protocol is federated and everyone can run their own server, but its not worth the effort imo so we could just use the one on matrix.org.
Matrix also supports bridging, which also has been used with discord, so people can use discord or matrix and be on the same channel.
Me and some of my friends use it extensively for gamedev talk, it satisfied all our needs so far.