in the modern age of Forums not being as popular, Discord (rip IRC) communities seemingly occupy this space now - they can be quite cozy, and give off a lot of the old vibes
Not even close. Discords owns your data and once the so-called-Discord-groupchat (server my ass, is NOT a server) closes down, you are out.
WIth Usenet your posted data and articles/discussions could be in your hard drive forever.
With Jabber and IRC you could bring your chat client, anything. Heck, even MSN/AOL supported several clients, both graphical and terminal, such as AMSN, tmsnc, Gaim/Pidgin, Miranda IM...
I miss that cozy weird familiar and insane place.
OTOH, 20 years ago my only concern was school and I had the energy to pull all-nighters. Now I have to pay my bills.