1. No politics
2. Nobody trying to sell you something or promote themselves
3. Based around a single, external topic, usually an established IP
Examples: r/Factorio, r/asoif,
I'd agree and say I don't think reddit has the quality of discussion in posts or comments that it used to.
For a venture-backed site even hitting a 20% growth rate per month would be a warning that you're not growing fast enough to justify continued investment, as was the case for a recent postmortem on Gumroad [1].
Given that this post was from 10 years ago that's definitely not the case for Hacker News, but in this climate it's gotten even more extreme if you're relying on venture backing.
If you have a constant user base that provides constant profit why is growth needed to sustain a business?