I can imagine a world in which a powerful entity (basically, the DM) expresses their subjective moral framework as a cosmic ought, and coerces their players to agree, yes. I cannot imagine a universe in which morality exists as a substance or law absent some sort of authority, no. Furthermore, I don't think it is possible to imagine such. I think that it is possible to tell yourself that that's what you are doing, but when you look closer you will see that it relies upon an assumed authority.
I think there probably isn't a lot for either of us to say as we seem to be coming at this from very different points of view. But I don't think this has to be a coercive thing. Some people genuinely enjoy cosmic oughts in their games. That can come from the GM, from the designers, even from the players all agreeing what those oughts ought to be. It can even be randomized.
On whether you can imagine something like this, or whether you can imagine an object of evil, the idea that you can't still seems to me rather silly. No one is saying you have to imagine an evil sword at the cellular level or an all powerful God. Can I understand and fully comprehend an all powerful cosmic ought? No, I am a finite being, but I can conceive of the concept and imagine it in a fantasy world. Just because our understanding of such things falls short, doesn't mean they aren't worthy to imagine in fantasy games, fiction or movies. This just seems like an odd restriction to place on imagination, art, games, etc to me
I'm not just tilting at windmills. I think the alignment system creates a lot of arguments and is fated to always create a lot of arguments, because it rests upon very shaky foundations. It's basically a system of virtues ethics, disguised as cosmic forces. If it works within a copacetic group, then awesome. I personally feel that it only adds confusion to the game (see many examples in this thread). Most RPGs don't have an alignment system, and don't miss it; had D&D never had a formalized alignment system, we wouldn't miss it. Writers don't use an alignment system to depict realistic characters and moral conflicts; to the contrary, it is hard to imagine any writer worth their salt going anywhere near an alignment system.
I wouldn't argue that alignment doesn't cause arguments. It clearly does. I personally think D&D alignment as it has been expressed over many editions, with maybe the exception of the old Law and Chaos approach which I think is simple enough to work, is strange, and doesn't reflect real world moral systems well at all. I don't think that stops a lot of people from enjoying it, and I can embrace the conceit if others want to. I don't mind it in play, if I am playing D&D but there is no getting around how weird it is.
I would push back on the idea that cosmic forces can't be imagined to be aligned with various ethical principles (real world religions do this all the time, and sure they ought to be fodder for imagining a fantasy world inspired by myth and legend). But the specifics of the D&D alignment system are wonky, I would concede.
I would still say some form of alignment system essential to D&D. At least for me. And alignment can be easy shorthand for characters. But I agree most games don't use it and it isn't missed in those (but then most games don't use Vancian magic either but you take that out and I dont' feel like I am playing D&D anymore).
I agree writers wouldn't use alignment. However the alignment system is drawn from fantasy sources like Three Hearts and Three Lions. I would argue it works in those contexts. But that also wasn't wonky like AD&D alignment. The D&D alignment system was invented for a game, I don't think that something intended for a game necessarily is going to work for fiction. If you go back and read those AD&D novels from the late 80s into the 90s, there was a period where they embraced brining the game mechanics into the fiction and it got weird (the example I often point to is Drizzt being told, when was on a quest of self discovery, by another character that he was a ranger-------it felt very odd). But again I don't think what writers do to address morality and conflict is necessarily something GMs or players are looking for in their dungeon crawl games.