Typically, the clients for discussions were fairly different from the binaries-only clients used today. Microplanet Gravity and 40tude Dialog were the big ones back then. Nowadays, only a few are maintained, but if you’re interested, I recommend Pan (or slrn if you’re comfortable with text mode). Finding active discussion newsgroups is a challenge on the modern Usenet though, it feels like trying to find a few survivors around the ruins of abandoned groups. A huge advantage of Usenet back in the day was when using dial-up internet, which used up your home phone line at the time. There were some parts of the world where you paid a flat monthly rate, but in mine and most others you paid by the minute. Using Usenet clients, as well as POP3 clients for email, you’d just connect to the internet, download everything and disconnect, then read everything, write your answers, reconnect to the internet and send/receive. Very efficient, and one of the reasons why despite some issues it had it held up until the 1-2-3 punch of the mass adoption of high-speed internet, social networks, and modern form of smartphones. Email is probably the only surviving old protocol that is despite webification still used by a large amount of people directly using separate clients. In a way, Usenet and IRC were also just that, protocols, with free and open source implementations. Back then most servers were maintained by ISPs and educational institutions, and sort of like Lemmy, your local Usenet server would also sync up with big groups out there. Discord is, again, a singular service - at risk of enshittification and failure, like Reddit, and any tech company. To me, federated and decentralized stuff like Lemmy, Mastodon, Matrix etc. does seem to have a lot of a spirit and resiliency of old-school ideas we had with Usenet and IRC back in the day. The biggest hurdle back then (and now, for fediverse) is getting a critical mass of regular people on here, not just free software enthusiasts or early adopters. It’s something that major social networks are very, very good at.

If basically feels like reinventing Usenet, with maybe some extra modern features

I did actually check if Usenet activity was back up, at least on the groups I used to be active on back in the day… unfortunately, nope.