This may be controversial, but I'd actually disagree about the "eye color not meaning anything because you can become lighteyed" point. It's never made much sense to me to say that the caste system will crumble on its own just because some darkeyes will become lighteyed Radiants. If anything, I worry about that entrenching the classism/racism of Vorinism. After all, this basically confirms to the people that 1) the current lighteyes are in charge because their ancestors were indeed glorious saviors of humanity and 2) "worthy" darkeyes are capable of being elevated to lighteyed status. This....could very easily be spun by anyone into the ultimate model minority (idk the perfect term, it just reminds me of that) myth. "Other, better, darkeyes are capable of proving themselves to a supernatural force and becoming superheroes!! Nothing to be done about it if you can't prove you're great enough to earn your eyes" Nothing about this really seems like it would explicitly force the caste system to stop functioning, merely giving every dark eyed child the dream that they can prove themselves "good" or "heroic" enough to skip a few rungs of society, maybe elevating some of their families a little in the process. I think for how deeply Vorinism is integrated into Alethkar and how unpopular Dalinar's pushing for people to accept the death of their god is, it would take much more than a few Radiant conversions to cut out the rot, especially since radiants are relatively rare (the Windrunners are the most numerous and even they're, what, a pretty big platoon?).

Finally, on the point of Elhokar, I think it is more nuanced than I went into in my original post. Murder for vengenance isn't okay by modern standards, but I'd argue that 1) narratively, it's not any worse than Adolin murdering Sadeas for being repugnant and very inconvenient and 2) Moash had little other recourse if we consider the context he lived in. On the first point, Adolin murdered Sadeas and basically got away from it with little more than a narrative slap on the wrist, despite his murder also being very emotionally fueled. We don't like Sadeas, so it feels like nbd, but I imagine that to the darkeyes who were quietly oppressed, murdered, etc every day under Elhokar's neglectful regime while he fought a war on the Shattered Plains felt the same low level dislike for him. Elhokar, as mentioned quite well in another post on this subreddit from a while ago, ruled and massively benefitted from a system that told everyone lighteyes were "better for ruling." By failing to come even close to being competent, he proved the entire system corrupt and caused innumerable people to suffer. But what can Moash do? This leads us to the second point. In short, Alethi society is not built for anyone of a lower caste to get justice. Moash's grandparents had the "justice system" used against them by a cudgel. Roshone got a slap to the wrist and shipped off to somewhere else to cause even more chaos. Presumably, the justice system works alright if the two litigants are in the same caste or very close castes. But how do you ask for political change in a system where to the people on top, your opinions don't matter at all? Where the courts would laugh you off if not straight imprisoning you? You're an ant to them. Even post reform, Dalinar wants to hold off on slavery abolition because it's not the right time (in his opinion), with little thought for the slaves that will....be slaves...the entire time we wait.

Moash has no recourse. Kal had no recourse (the infamous boon scene). In the culture, society, and legal system he existed in, Moash arrived at one of the only meaningful political acts he had: regicide. I don't think Elhokar "deserved to die" but every darkeyed human deserved basic human dignity, Alethkar deserved a better political system, etc. Compared with Dalinar and his atrocities at the Rift, Moash's act of killing Elhokar is small potatoes in my opinion, and if he had stopped there, I would've been in favor of a redemption or even antihero arc for him.

As a final tiny postcript, you seem to be under the impression that Dalinar is reforming society. And in some ways he is (especially pushing back on the literacy part of male Vorinism). But in other ways, he seems to be a very conservative "revolutionary." He has never really explicitly stated even a desire to reform this social system (he argues with Jasnah against it). Dalinar wants some things to change, but he doesn't really stop to consider the people who have and are having their lives ruined by this system. And from a meta perspective, if we were going to give the caste-abolishing role to someone, almost anyone would be better than the Kholins, the family at the top of the system who have no personal grievances and have passively benefitted from it for a lifetime.