Slashdot has been a walking dead version of its' former self once it sold to SourceForge.
I think it slid into gradual irrelevance in the following decade, but I'm not sure there was any one moment that did it. Personally, I'd date its decline to 2011, perhaps not coincidentally shortly after founding editor Rob Malda left.
I'd never heard of Soylent News. I can't decide if I love or hate that name. :)
HN is the closest I can get to a replacement.