The friends list is inconsequential. It's for sending private messages to people you already know and met from a Discord server. Long running group chats are an aberration, people just start up micro-discords instead.

And that is what Discord alternatives will have to solve - the ease of setting up a new Discord "server" by any old random user is hard to beat in terms of convenience. Matrix is the only real alternative on that front.

However, if you have an established community and have at least a little hosting knowledge among the staff, the moat is shallow to nonexistent, and it's just a matter of how much of a pain in the neck Discord decides to be.