Objective morals implies something metaphysical.
Maybe. I know atheist materialists who insist on objective morality using "science" as the higher authority which imposes on the individual obligations.
Such might exist in Middle-Earth in the mind of Ilúvatar, but even the Valar do not know it.
Whether not Valar know it are not doesn't matter, in Middle-Earth there is objective truth as revealed through Illuvatar - Tolkien's continually reflected metaphor of light. This isn't a world of subjective morality no matter how hard you try to spin and dig out of it.
Tolkien's morals are pretty clear..
Let's be clear and accurate here. Tolkien is a fanatically pious Catholic on the scale of someone like Isaac Newton. This is a guy who broke off a friendship with his best friend because his friend married a divorced woman, a sin he found too painful and overt to bear with. Tolkien absolutely believes in objective morality of the most concrete sort. This is a guy whose own standards for himself were incredibly high and his expectations for the behavior of others were equally high. But this is certainly not a guy who thinks he is his own moral authority or that he gets to decide what is right or wrong.
yet even he often writes about morally grey people and about good people struggling with moral choices without obvious correct answer.
Look 'The Bible' itself writes about all sorts of morally grey individuals from Abraham and David to Peter and Paul. That Tolkien would think it entirely appropriate to have stories of morally conflicted and compromised characters in no fashion means that he isn't advancing an objective morality and coming from a place of objective morality. Do you honestly think that people who believe in objective reality don't deal with the messy reality of people in the real world? Really? Nothing about believing in objective morality means that you can't have morally complex individuals making hard and difficult choices.
You also said something earlier about objective morals being able to exist even if they were not known. It think that is meaningless.
Of course you do. But again, you have come hard on the Chaotic Neutral spectrum where morality is all about your internal subjective reality and decisions. But what makes objective morality objective by definition is that it applies to you whether you know it or not.
But what makes alignment system weird is that it indeed is completely knowable.
This isn't weird. This is pretty darn normal. In most fiction the author expects the reader to share with him knowledge of what is right and wrong based on conventional understandings of what is moral. In most fiction, the correct course is action is presumed to be known by both the reader and the character, and the difficulty is that the reader is supposed to understand that doing the right thing is much harder than knowing the right thing to do. In fact, the author generally assumes that the reader has had the experience of knowing the right thing to do and then talking themselves out of doing it and doing the very things that they believe to be wrong. The reader is supposed to understand that moral high callings are difficult and require great willpower and sacrifice and courage and hope and faith and other virtues, and that failure to reach those high marks is a normal part of life - which is why we celebrate heroic moments. It's not because we think knowing the right thing to do is hard. It's because we know that having conviction and belief in that moment is hard. That's the experience conveyed by most heroic fiction, and not that the truth is ineffable or uncommunicated.
This is something that is extremely rare in any other fiction, if we do not count actual religious texts.
No, it isn't. Because for one thing a great deal of fiction is inspired by one sort religious text or another. Much of Western Fantasy is either directly inspired by a religious text or a response to it.
And I don't think this sort of moral transparency is a good thing at all. It destroys ambiguity and ethical nuance. Even I stories with somewhat black and white morality, the shades are never this uncomfortably stark.
This is an opinion. I don't think it's a surprising one for you to have, but there it is. Those are your words.
That is absurd. Words mean things.
Absolutely I agree, though that's a pretty darn strange thing for a moral relativist to believe.
People rarely believe that they're not good (sometimes people accept that they have failed to reach their own moral standards, but they strive to reach them.)
I believe that I'm not good. In the circles that I frequent believing that you are not good is normal. But I think what you mean is actually that people rarely believe that the things that they believe are not good. And that is a little rarer, but it's not very rare.
What I've been writing about is a fictional reality. You refuse to accept the fictional reality because it doesn't conform to your moral beliefs in much the same way that many Christians would reject it for its occult influences, magic, and paganism, but the things I've been talking about have strong parallels in the real world.
In the setting "Good" is defined conventionally by things like mercy, compassion, and charity. The reasons for nomenclature are obvious. Those sorts of things are good across a wide variety of moral systems including the most prevalent Western ones. Those are things that most people expect to be good without questioning. Yet in the real world many people can and do argue that traditional virtues like mercy, compassion and charity are in fact wrong. We can make arguments against all three of them and point out real world examples of cultures and religions and philosophies that concur with this judgment against "Good". For example, Objectivists believe things like self-sacrifice and altruism are moral wrongs. Now if we are going to talk about that in a useful way we need to distinguish between the virtue system that upholds mercy, compassion and charity from the ones that don't. D&D in the great wheel cosmology does that. So, yes we have plenty of examples of people thinking that "good is wrong". That "good is wrong" or could be is not a hard concept, regardless of how you think people tend to talk. It's no more confusing to someone at first than a statement like "compassion and charity are evil", but that later statement would certainly be more confusing in the context of the alignment system.
And in any event, this is the thing that is actually written into D&D from the start. Evil people believe for reasons that I could explain that Woe is better than Weal, and that for them Evil is their good. And Chaotic people likewise believe that correct and right action is not Good, but Chaos. A Chaotic Evil person in D&D doesn't believe that they will be punished by their actions because they broke objective moral tenants. They believe they are following in the example of right-minded paragons who will eventually prove their rightness by triumphing over the false and weak beliefs of Good.
It's baffling to me that you'd look at that system and claim "It destroys ambiguity...black and white morality...uncomfortably stark". That's such a bizarre take on the system, which in fact as I noted is actually in the standard cosmology massively ambiguous and gray with no answers for you just options. Is it better to go to the Nine Hells or Olympia? Well, that's depends entirely on your point of view.