The real reason so many people use discord is the network effects. My friends and I joined discord really late in the game but for various reasons we eventually needed it. Eg, game development discussion groups and eventual marketing, or your weekly dnd group uses it, school, etc

I hope this succeeds but it’s going to be hard to take market share. I hope the signup flows and Ux are really smooth, foss software is often pretty hard to get started with for non technical people