Any intellectual community will have (at least implicit) norms surrounding which assumptions / approaches are regarded as:

(i) presumptively correct or eligible to treat as a starting premise for further argument; this is the community "orthodoxy".

(ii) most plausibly mistaken, but reasonable enough to be worth further consideration (i.e. valued critiques, welcomed "heterodoxy")

(iii) too misguided to be worth serious engagement.

It would obviously be a problem for an intellectual community if class (ii) were too narrow. Claims like "dissent isn't welcome" imply that (ii) is non-existent: your impression is that the only categories within EA culture are (i) and (iii). If that were true, I agree it would be bad. But reasoning from the mere existence of class (iii) to negative conclusions about community epistemics is far too hasty. Any intellectual community will have some things they regard as not worth engaging with. (Classic examples include, e.g., biologists' attitudes towards theistic alternatives to Darwinian evolution, or historians' attitudes towards various conspiracy theories.)

People with different views will naturally dispute which of these three categories any given contribution ideally ought to fall into. People don't tend to regard their own contributions as lacking intellectual worth, so if they experience a lack of engagement it's very tempting to leap to the conclusion that others must be dogmatically dismissing them. Sometimes they're right! But not always. So it's worth being aware of the "outside view" that (a) some contributions may be reasonably ignored, and (b) anyone on the receiving end of this will subjectively experience it just as the OP describes, as seeming like dogmatic/unreasonable dismissal.

Given the unreliability of personal subjective impressions on this issue, it's an interesting question what more-reliable evidence one could look for to try to determine whether any given instance of non-engagement (and/or wider community patterns of dis/engagement) is objectively reasonable or not. Seems like quite a tricky issue in social epistemology!

From my own experience and from what I've seen, I think it's common for new contributors to the forum to underestimate the amount of previous work that the discourse here builds on. And downvotes aren't used to disagree with a post, but are supposed to be used as something like a quality assessment. So my guess from a read of your downvoted post is that the downvotes reflect the fact that the argument you're making has been made before on the forum and within the wider EA community and you haven't engaged with that.

Maybe search for stuff like "AI-enabled coups", "power grabs", and "gradual disempowerment".

I can't see the downvoted comment in your comment history. Did you delete it? 

By the way, did you use an LLM such as ChatGPT or Claude to help write this post? It has the markings of LLM writing. I think when people detect that, they are turned off. They want to read what you wrote, not what an LLM wrote.

Another factor is that if you are a new poster, you get less benefit of the doubt and you need to work harder to state your points in plain English and make them clear as day. If it's not immediately clear what you're saying, and especially if your writing seems LLM-generated/LLM-assisted, people will not put in the time and effort to engage deeply. 

Observations:

1. Echoing Richard's comment, EA is a community with communal norms, and a different forum might be a better fit for your style. Substack, for instance, is more likely to reward a confrontational approach. There is no moral valence to this observation, and likewise there is no moral valence to the EA community implicitly shunning you for not following its norms. We're talking about fit.
2. Pointing out "the irony of debating “AI rights” when basic human rights are still contested" is contrary to EA communal norms in several ways, e.g. it's not intended to persuade but rather to end/substantially redirect a conversation, its philosophical underpinnings have extremely broad and (I think to us) self-evidently absurd implications (should we bombard the Game of Thrones subreddit with messages about how people shouldn't be debating fiction when people are starving?), its tone was probably out of step with how we talk, etc. Downvoting a comment like that amounts to “this is not to my tastes and I want to talk about something else.”
3. "I started to notice a pattern — sameness in tone, sameness in structure, even sameness in thought. Ideas endlessly repackaged, reframed, and recycled. A sort of intellectual monoculture." This is a fairly standard EA criticism. Being an EA critic is a popular position. But I think you can trust that we've heard it before, responded before, etc. I am sympathetic to folks not wanting to do it again.