My friends and I started a website devoted to a multiplayer game back in college at the turn of the century. It had a forum that was heavily used.
Somehow, 20+ years later, it's still going. 14 million posts and 196 people online now. And the game series has been dead for over a decade. I moved on a long, long time ago, but many people remain.
There's a community there that just keeps going, despite the original purpose being long gone. I don't think that would happen with Discord.
I don't know if one can easily say what would or wouldn't have happened if you had chosen a different platform. There are a lot of communities based on irc that have existed forever.
