This. I loved usenet, but when the spam started, that was the harbinger of doom. Maintaining communities costs time and effort as well as servers and bandwidth. Given the thankless task of fighting the onslaught of spam, trolls, raids, organized information ops etc it's not viable as a volunteer exercise in general. It can be done by mutual cooperation and self-policing on a small scale in isolated groups of like-minded folks but en mass the incentive to ruin the commons for everyone else will always be too strong for some folks.