

Replying to this before OP asks.
Usenet is distributed across hundreds (thousands maybe?) of servers. It’s centralized in that setting up your own server and getting the same access as joining an existing Usenet server is going to be very difficult (and with Usenet being used for privacy more and more, could be impossible due to admins not trusting a random new person), but in theory one could.
So everyone else has good points but there’s one other part I don’t think was mentioned.
Most ISPs use a PON based network. This lets them connect one fiber in their network and “split” that to up to 128 (or more, depends on the OEM) customers. You need a either GPON (Gigabit passive optical network) or XGS-PON (10 gigabit symmetrical passive optical network) SFP module and usually the ISP has to get a serial number off of that module to provision the proper data service.
This is contingent upon the ISP being willing to do that. The one I currently work for, we really don’t do that except for businesses.