Some loosely organized thoughts on the matter:
I feel like a lot of you guys that are so against Discord have never tried it. I started using Discord around January for a few different subjects and I was very pleasantly surprised by how versatile it is. I had resisted joining because everything about it just sounds like a new Teamspeak or Skype which I had no interest in but I've actually found that it's not simply just another chat application. I've been in Discord servers with hundreds and hundreds of members that are run much more like a forum than a chatroom, and in fact most of the heavily populated Discord servers I've been in are better moderated than this forum. I've encountered such large servers that have literally no presence outside of discord. Hundreds of people organically forming a community exclusively inside of discord that works at least as well as any forum would. It's quite interesting actually!
Discord servers can have as many different voice and chat channels as needed for various different categories, just like subforums. If you made a discord server for this forum you could translate all of the subforums to discord channels nearly one for one without issue. Additionally, because messages are stored perpetually you can scroll up to find what you need pretty easily (the search actually works also). While I haven't been in any ant discords I readily believe that you could get very good help in a populated discord.
Despite how cool Discord is I wouldn't advocate for the replacement of a forum with a discord server. Discord servers are still terrible for long form content like large posts and ongoing threads such as journals. They are as far as I'm aware not indexable by Google and so their content lives and dies as the startup that makes Discord does. Similarly the forum chat does not have the potential to replace the functionality of a Discord even if Drew went out of his way to purge it of the nonsense it's currently filled with 80% of the time.
Rather than thinking of Discord as drop in replacement for the chat, think of it as a hybrid between forums team speak. I see no reason why they can't coexist.