Totally disagree with your first point. It is only valid if you have infinite money and all the best connections and perfect trust. Show me where that exists and I’ll buy it.
Hiding the right secrets in an early company is critical, whether they are technological that you are hiding from competitors or business plan endgames that you are hiding from customers (but perhaps you aren’t aware of them and only the VC sees it). There is a big difference between some person thinking they have a great idea but won’t tell anyone, and determining where you draw the line on sharing product, go-to-market, etc. People who raise enough money have the “that’s the secret part” point of the conversation. The conversation goes better if they communicate that in a way most people don’t notice, though, and so at that point they frequently redirect, deflect or defer.
I think we see the audience of HN differently — from my perception it is predominantly aspirational entrepreneurs, not actual entrepreneurs that make up the majority of engagement here. While no doubt the percentage of entrepreneurs is higher here than just about anywhere else, entrepreneurs have less time and there are just far fewer of them. What I believe is predominant here though, whether entrepreneur or not, is engineer/developer roles.
Regarding your point on competition I think we understand the two cultures of engineers and writers differently. Writing has less constraint, and in my experience that means it is more reliant on ego expression. It can be humbling but a person can also make a great career being a terrible writer. Engineers make things that function. If you are a terrible engineer, your work will rapidly disappoint probably a lot of people, and either you improve, you hide somewhere adjacent, or you leave the profession.
I think HN works for a variety of reasons including the general humility of engineers, the general lack of desire for the spotlight, and the frequency of dramatic and immediate improvement of workflows due to new tools. I don’t know which of these and other reasons are critical but I am skeptical writing has enough of them. Maybe with a new generation of writers.