"Since HN has a focus to begin with, I am not sure how helpful it would be."HN has focus... in theory.
But even according to the guidelines, what's on topic is:
"Anything that good hackers would find interesting. That includes more than
hacking and startups. If you had to reduce it to a sentence, the answer might
be: anything that gratifies one's intellectual curiosity."
In practice that allows for a very wide range of stories, even when those submitting and voting on the stories bother to read or follow the guidelines.
And that leads to the very problem tags are intended to solve.