Right.... how is that different from IRC other than being controlled by a big company with no exit ability and (again) extremely tenuous privacy promises?

For the text chat, it's different in the way that it lets one make their own 'servers' without having to run the actual hardware server 24/7, free of charge, no need to battle with NATs and weird nonstandard ways of sending images, etc.

The big thing is the voice/videoconferencing channels which are actually optimized insanely well, Discord calls work fine even on crappy connections that Teams and Zoom struggle with.

Simply put it's Skype x MSN Messenger with a global user directory, but with gamers in mind.