Well, at this point the mainstream usenet network is dedicated to piracy. That's what it is - 100% piracy. The only reason they use NNTP instead of something like BitTorrent and call them "articles" instead of "files" is to maintain plausible deniability that that isn't what they're doing.
The textual discussion network may as well be its own wholly separate network. I only know of Eternal September, but I'm sure there are other servers.
I think that's where the "build your own network using nntp" comes in