These things are still there, I occasionally peak at newsgroups from time to time (there are free providers for the text trees) they're just not growing. IMO a lack of growth these days is probably a good thing.
And then the masses got onto the Internet. Lookup the term "Eternal September" [1]. The whole culture got overwhelmed by people that did not value the medium. Spam got out of hand, trolling was a most popular pastime. That killed Usenet, as normal discussion was impossible.
Can Usenet be revived? Not while there is money to be made on the Internet. Any attempt to gather people online gets perverted by someone smelling money.
Usenet was great until the mid-nineties.
It likely will. Give it some time for more internet screws to be tightened around the world. Once people see the screws had Loctite applied they will find more alternatives and revive older transports protocols. It is still the vastly superior medium for automatically downloading massive amounts of multimedia content if one filters on pre-shared subjects preshared secrets, GPG signed messages. The spam can be entirely automagically ignored.
For all their faults, big tech do mostly moderate their sites to the extent you won't find illegal things there.
Having multiple moderators of content, and multiple dimensions of moderation (think tags with attached scalar multipliers) could possibly work. Each host of the feed could then just not store anything that fails to pass as legal in their jurisdiction, or fails to meet their moderation policies.
Regardless of its arrangement, any large cooperative collection of stuff, albeit in a feed like usenet, or forums, or a files store, multidimensional ranking/moderating/reputation management is the way to go, IMHO.
I don't remember what premium services I was aware of once upon a time (vipernews?), but something like $10-$20 bucks a month was good for pirating stuff if you were ever into that. Not sure how that scene is now days.