There are ways to get good comment fields without having them be babysit by an editor-appointed moderator, or by promoting self-selected moderators from the users.
It’s just that most media aren’t interested in trying them out, because that would mean giving up editorial control ever so slightly. They would rather have a bad comment section they can complain about, than a good one which might not agree with them.
The core problems were solved back around 1998–2000. Rob Malda’s Slashdot fixed one part of the puzzle by randomizing/rotating limited mod privileges. Raph Levien’s Advogato solved the other part of the puzzle by coming up with effective protection from Sybil attacks.