I see Discord being used for things where forums (and non realtime conversations) used to rule supreme, like hobbies, tutorials, etc.
Why? A tutorial is not a real time chat. A showcase of hobby projects isn't a real time conversation either. And the searchability of these tools like Discord is terrible. I really don't understand why this terrible thing became popular.
Discord is absolutely terrible at storing semi-structured information like a wikipage and I don't see them fix that without completely overhauling their entire service (although I'm sure they'll try and muck up the death of publicly available knowledge even more).
(I guess wiki comments and especially talk pages can work too, but they are terrible and not the place for community discussion.)
I'm not sure Discord is necessarily good for "gaming communities". I mean, Discord is live chat. This is good for some aspects: match making, news, etc. - anything that has a short lifespan. However, a lot of things about games don't. Wikis are perfect for publishing this info. Think of a Street Fighter type game. Characters have their move set, that doesn't change. Imagine having to search through discord for how to do a fireball with Ryu. Then there's strategy - that changes, albeit periodically, after tournaments, etc. By all means, this stuff can be discussed in discord, but the consensus strategies have to be published because it's a terrible experience to search through chat logs and follow along with long finished conversations over who knows how many posts, figure out context, etc. compared to just reading it on a wiki.