The shittiness of a social news site has nothing to do with the any sort of enforcement or criteria for a topic, or even having a topic at all. Rather, things go to shit on a social news site when the
community is composed of people who can't (roughly) agree on what they like to read.
To regurgitate an old adage I heard from a Dungeon Master: "It's not the game that's fun, it's the players." We're here to share links and talk about stuff, not to "post" and "comment", blind and deaf, into the void. As long as we all like one another, the site is good. When we attract a group of people we don't like as much, and those people attract people we don't like at all, then the site will suck, because those people won't be sharing and talking about the same things we want to share and talk about.