And then there were these guys called Tom and Steve. And they wrote Usenet. And all was well until September fell. And then the usenet gradually faded into obscurity, as users moved towards walled gardens, and away from netnews. Some of these users were weeaboos: This is how the -chans made their way here from Japan.
Usenet was created because "networks" were expensive and "fax lines" were cheap. If you did it correctly machine A could call machine B in its local calling zone which could call machine C in its local calling zone and a message could go from A!B!C!user without incurring any long distance charges (aka "free").
Because you would lose your news feed if you pissed people off, spam was low because no admin would tolerate one of their users putting their system at risk of disconnection.
When networks because "free" and anyone could talk to anyone, there was no impediment to spam and no way to scale, and much of the infrastructure collapsed on itself.
That said, there is absolutely nothing preventing anyone from creating their own peer to peer messaging network. They could re-use the netnews code or write their own with a bit more security built in. The argument to that is "but hey no one will use it." to which you say "Who cares? My friends and I will use it." and since it is free and it is just you and your friends it will be fun and enjoyable. And if you're very unlucky everyone will join you.
I sure as heck hope that everyone doesn't join me in my communities: the magic would go away.