You shouldn’t interpret this sites focus as the people that post here not thinking there are more important things.
For this reason I tend to browse HN using the https://news.ycombinator.com/active frontpage because it contains the flagged topics that certain users of this site attempt to hide, while also preserving the vast majority of interesting tech-related topics.
>On-Topic: 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.
>Off-Topic: Most stories about politics, or crime, or sports, or celebrities, unless they're evidence of some interesting new phenomenon. Videos of pratfalls or disasters, or cute animal pictures. If they'd cover it on TV news, it's probably off-topic.