Our users do seem to like Discord, we also have a Matrix and IRC but those are dead too. Discord is where our users seem to flock to.
What is really happening is that people are looking for documentation or support, seeing that the forum, the IRC and the Matrix are dead, that the only other thing is discord, and give up. Minus some fraction who already use it for other purposes (gaming, probably) and don’t mind using it.
But from your perspective, it looks like everybody is joining discord and liking it, because all of the other people just give up. It’s only a very particular demographic that uses discord. Most likely (I might be wrong, but this is what I guess) very young, male, gamer, european descendent, and from a relatively wealthy western country. That’s a very small part of humanity.
If you as the maintainer go and use the forums, and maybe announce this in discord, the users will follow.