Most people are on Discord, joining servers has very little friction (no separate accounts), there's decent bots and mod tools and such, ability to create as many channels per server as you want (e.g. for discussions, media, music, whatever) and participate in text based conversations more or less live. It's also easy to jump into a VC and chat while you play games with friends, share screen, stuff like that.

Most alternatives suck for that purpose. There is search for server members and the "blinking things" keep you up to date with where the new stuff is and I presume give you dopamine hits. It's simply not old school forum software and considerations that'd make sites like that good don't enter the equation at all - which also makes attempts at turning Discord into a support forum for any "organized" group or project misguided at best, but also great for the more casual gaming/interest oriented communities.