No, you're absolutely right. Discord is incredibly impermanent. Besides the lack of being able to search for things or split conversations into separate threads for every topic because it's a chat tool, not a forum, as soon as a server disappears, everything hosted on that server goes as well (as far as end users are concerned. I'm sure Discord can pull stuff from their backend).
We need a return of niche forum communities and the like for the sake of the preservation of information.