They patched that bug in October, didn't you know?
https://www.techradar.com/news/discord-has-patched-a-critical-security-issue
As for the thread topic... I use the discord a lot. It is especially useful for finding the fandom of so called "problematic ships", such as incest pairs, age gap, kinky stuff, and so on. Most of those people get chased out of regular fan spaces (for being "gross"

) and so they are essentially hiding in private servers. There are discord servers for everything, from game translation projects, to individual fan-fictions.
As for AarinFantasy, does it need a discord server? I feel like forum based communication is dying off in favor of instant messaging platforms. I mean, it's been like this for close to a decade, just slowly growing worse.

Whether this means the death of AF, I don't know. (and I don't want to think about it!)
I don't know any general subject Yaoi servers though, for what it's worth. Only specific fandom or ships.
Eh? Dated? But they do an update nearly every week...?
Anyway, Discord is what you make it. If you join a terrible community, nothing forces you to stay. People will make their drama anywhere online, facebook twitter you name it, there's drama there! And unless it's super specific or unpopular, odds are that there are probably at least two or three other servers for whatever you are interested in.
Or if it's minecraft, there are iike 9001 servers lolz