All cultures that promote discussion tend towards biases, status quos, and shutting down revolutionaries. That's part for the course of coexisting as human beings. Each society forgives some things and prohibits others. Each society has some topics which are difficult to discuss rationally within that society, requiring much more heavy-handed moderation than other topics. HN's specific set of such topics
can be particularly unusual ("/e/" is an example), but as you correctly indicate, it's difficult to discuss race and wealth rationally too.
Open dialogue is a platonic ideal of how a community can try to be. No community can deliver perfectly that ideal, because every community must compromise that ideal if they wish to continue functioning rationally — both when there are disagreements over strongly-held views, and when there are malicious actors who seek to exploit the platonic ideal of openness for a dizzying number of outcomes.
It's fine to declare that HN has these properties, but it's also important to remember that all social communication systems share these properties. For example, in my opinion [1], the voting system used on posts and comments here biases the site away from rational discussion when malicious actors use downvoting not to silence irrationality, but instead to silence rationality that they disagree with. I think this is a critical flaw in the site. In a sense, my view intersects with yours; we both consider voting to promote 'status quo' behaviors, and we could probably discuss at length what 'status quo' means and whether that's the right phrase for both minority and majority views.
The mods do their best to ensure that unpalatable but rationally-presented viewpoints are given their due consideration, but it's very hard to overcome the problem of "downvote to disagree", even when it's a blatant guidelines violation, without risking the essential nature of HN as a discussion forum centered around upvoting. The mods are, when I email them about instances of this, willing to communicate with me about what I perceive as malicious behaviors within their forum, while also recognizing that the site does not always deliver on the ideal of open dialogue.
In my estimation, delivering perfectly on the ideal of open dialogue, would require a human moderation council that considers every single post and comment in realtime before it goes live, deduplicates redundant comments into upvotes, binds together related topics into topic-focused headings, and actively shuts down conversational warfare (such as sealioning and others). This would, without fail, have biases and a tendency towards status quos, just as HN does today. They would be different biases, but they would still fail to deliver perfectly on the ideal of open dialogue.
Whether the site delivers a form of open dialogue that is acceptable to you, or to me, or to others — that's absolutely up to each of us to decide, and it's probably something we can't discuss very rationally, because what community can consider itself rationally without bias? None that I've met to date. But the mods have built in enough safeguards to try and protect those who question the mods. It's not even remotely perfect, and it's certainly not heavy-handed enough for my tastes, either. But the sum of moderation approach, and biases, and loudly-held viewpoints, and flaws, and to what degree open dialogue takes precedence over social compromise — that's what makes each community unique.
So I do support you in describing the flaws of HN. Yes, "open dialogue" at HN is not given ultimate priority, is not inlaid as deeply as is theoretically possible. That's the price paid to have human communities at all. Whether HN's payment of that price is acceptable is worthy of discussion, but payment of that price in some form is universal. From that position, it's possible to rationally consider "is HN making the appropriate tradeoffs vs. open dialogue", and it's absolutely appropriate to say "I think the mods should intervene in this discussion, to counter irrational behaviors by the users, the mods, and/or the algorithms". If they don't understand the biases or status quos or other irrationality that you're pointing out, then that's a great time to provide proof, but certainly I think you're generally right.
There are a couple of points I've been "once or twice a year" emailing the HN mods about for what I suspect is probably several years now (I refuse to look), because occasionally I trip over some proof of something that I didn't have proof for, or I find some new form of an old problem, or I just feel so strongly that I open my email client and write them a plea to make it better, to bias the site towards "open dialogue" and away from whatever I'm seeing that's truly upset me. They do not reliably agree, and I don't expect them. I don't desire them to. I'd like someday to see the site deliver better at open dialogue, without taking away from what makes it uniquely HN, and whatever my opinion may be any given day, I do not envy them considering all of our opinions, and being responsible for the compromises that they have to make as leaders of this community.
I do not believe that I could run a community with fewer compromises. I would run a community with different compromises, and those compromises would draw objections about how I'm restricting "open dialogue", too. So that such restrictions exist here is almost uninteresting as a surface-level fact. It's how those restrictions exist here uniquely, or how they interact in unusual ways, or how they contrast with how I would have restricted things instead, that's interesting and novel and opens the door for me to consider and participate in such a discussion.
You haven't the time to prove in detail your beliefs, but I am happy to say that at least in a couple of your specific complaints, I agree with you, and I'm doing my best to convey my concern with proof when my limited time permits. I don't know if it'll help or not, and sometimes I go months without saying anything at all. But if you never end up having time, be assured that you are not wholly alone in being concerned, and that someone else is too. We may not agree wholly, but that's community for you.
[1] https://news.ycombinator.com/item?id=19745267