Discord haters look, it is simple.
Until Discord appeared we had
Ventrilo, Mumble, TeamSpeak, Skype, etc, etc
I've been using those for like 10 years almost everyday
They had voice chat, some had viable text chat, etc, etc.
And then Discord appeared which had:
Voice Chat,
Good text chat (images, code snippets, emojis, reactions, etc)
Streaming Video (!!)
File share
Robust bot integration
Lack of security problem unlike the self-hosted alternatives have.
This one is important in gaming communities in e.g MMORPG games cuz there's nothing better than being DDoSd cuz you left team or because you talked to somebody on wrong TeamSpeak server 5 months ago :)
Push2Talk - this is also important, I dont understand how e.g Teams dont have this shit.
Imagine you're working on remote with kids in the background - having an ability to push button and talk is really useful! So you don't have constantly mute/unmute yourself! Gamers have been doing it for over 2 decades but with the parents in the background instead of kids
One account between all servers with ability to customize your identity
All of that in one solution. That won its market.
Provide something as innovative and robust as Discord and people may consider switching.
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I know that IRC's simplicity may be beautiful for hacker's mind, but it doesn't solve my problems nor make my life easier, so I'm not going to use it over Discord.