Maybe we can use this as an opportunity to use different tools for different purposes. Text chat is the easy part, evidently. The issues seem to be around voice/video/group chat on one side, and forums/wikis on the other.
What we need to recognize for one thing is how Discord makes it easy to host info repositories, but sucks at making that stuff accessible. We need a decentralized platform that makes it easy for someone to sign up and create their own forums and wikis in a user-friendly point and click manner that Discord does, but makes those same hubs optionally public and viewable for users without having to join anything.
Then for more live-oriented stuff, Matrix is already the most mature, established, closest thing to Discord we have. We just need it to be better at voice, video, screen-sharing, etc. If I understand correctly, that's already being worked on.
Hell, maybe the former could very well be implemented on top of Matrix itself even.