What you call "off topic" has been very much on topic for HN for a long time. The guidelines clearly say what is on topic, and it's more than "start up stuff".
> 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.
That sentence has been in their since, well, ages.