? A newsgroups live on many different news servers, hosted by many different subjects, potentially including it's members newsserver. People who host server can choose what groups to serve and with what privilege (read only, max x post per days etc) but do NOT control posts groups content (posts/threads), any member can and normally mirror a (recent) snapshot of group contents on it's own personal spooler etc. Essentially no one can control the entire system.
A website typically run on a dedicated server, not mirrored elsewhere, under the complete control of it's owner, and hosting. So while no one really "own" usenet different subjects own, can censor, destroy etc a website and their reader can't really do much about that.
We have of course other types of site, ZeroNet is a nice example, but they suffer many problem, they are far less available and known compared to usenet and their "ownership" is still partially in singe subject hands.
A simple practical example: what happen to your HN post if HN disappear? How can you or us "posters" united can do in that case? Vs what happen if a newsserver disappear?
The internet as a whole: yea, anyone can spin up a site, though that's not really the point. By that logic Facebook is federated, since anyone can spin up a facebook-like.
Individual websites: the sole owner of the domain name determines all servers that can serve content, thus all behavior, which is pretty conclusively non-federated.
