Well you are right when you say that's part of the appeal of HN. The thing is, that's part of the appeal for a hacker. I bet that for a JS professional, part of the appeal of this site is to have restrict the news just to that domain.
At the end, the success or failure of these kind of web sites tend to be more related to the community rather than the look or the features.
Part of the appeal of HN is I get interesting stuff from all over (#) not just my niche.
TO do an HN, but have it on one niche seems missing the point.
(#) less of it now, these kids today, back when I were a lad ... shoebox .. motorway.