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.
replyAnd 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.
The discord servers my friends and I use are just for shit posting and using voice among like 10 of us. If it becomes annoying we can move to the next thing. We're all millennials. We can run whatever server if needed it's not a big deal.
replyIf you meet somebody mid match in a game like Valorant or Overwatch, it's simple to give them a username and they can add you and you then choose to group voice call vs inviting them to a private server, especially before you know them very well.
replyTeamspeak, as far as I know, doesn't have a way to solve this.