I guess the main points are voice chat channels, community building, bots, free, chat capability as well.
It was pretty attractive for gamers. Especially in the MMO section where you needed to get 20+ people in. Compared to in-game voice it was private as well, so you weren't talking for your entire lobby.
It's not just a text chat app/IRC replacement. There's no calling, just voice channels. Hop in the voice channel to join if you want to play/talk. It was good.
Looking at alternatives I still feel there's not a lot of competition for discord.
Sure there's matrix, but from what I gather online it's not the easiest to set up ( at least the voice ), most people aren't interested in self hosting this stuff or paying for it. There's IRC, but that doesn't have voice chat. Slack/mattermost has voice, but you need to start a call and it doesn't support 30 people.
Guilded.gg seemed to be a good competitor ( no experience ) but that has been discontinued. Now there's gamevox.com and rootapp.com that seem to be fighting for that market share.
Moving from one big corp to another though... I've looked into self hosting a teamspeak6 server on my vps for friends. Max 32 people. And I'm losing resources on my vps for it.
Discord was going to shite, but they're speeding up now.

