I'm a non-native speaker. I'm guessing you're saying the adjective is dated and reading it again it does sound like that. Still, i was trying to say 'faster than the usual fast'
Usenet was not historically real-time because of several things:
1. There were a lot of servers.
2. The servers were not arranged in an optimal network.
3. The network was full of cross links, many of which made no topological sense.
4. Not every server carried all newsgroups.
5. There were a lot of users, who read a lot more than they write.
6. Binary messages (when carried) grew to huge sizes (for the time).
7. Network links were very slow by today's standards.
8. Disks were slow, small and expensive by today's standards.
9. Every ISP felt it had to provide free Usenet service, but few of them did it well.
With modern hardware, Usenet could be as close to realtime as you expect email to be -- dominated by people's attention and writing speed. And carried over TLS, of course.
Exorbitantly fast?
Snappy responsive?
Real-time? (Haha)