Q: Why don’t alignment mechanics work in 5e?
A: Because alignment was a mechanic used in conjunction with a rarely used portion of the game.
Alignment in #dnd is not supposed to be a personality test but a simplified representation of how a character or creature relates to the cosmos in chart below.
A shift in D&D’s cosmology combined with the move away from a human-centric model for the adventuring party effectively broke how alignment worked.
While some people have argued that player-selfishness is part of what’s going on, you need to look at alignment not as a play-style but as a mechanic. The alignment mechanic represents an aspect of the world in which D&D is set. Trying to drop that mechanic into a different cosmology just doesn’t work without rebuilding the cosmology it represents from the ground up. It would be like trying to apply Tolkien’s concept of light and dark elf to other settings’ elves, bereft of any meaning due to the absence of the Trees of Valinor in said other setting.
Isn’t alignment just a reflection of the cosmos through a character’s behavior? To an extent, but not exactly. Alignment in D&D is not necessarily an indicator of behavior: a character can be “good” but not fall into the “GoodTM” column of a cosmology. Just look at the “virtuous pagans” in Dante’s hell.
For alignment to work mechanically as designed, it needs to be treated almost like a birth-sign. You don’t necessarily have to adhere to all of the associated tropes and traits strictly, but you need to assume, for game purposes, that there’s something greater in effect beyond your own understanding and control. You also might need a touch of Calvinism in your setting for alignments to work as designed, too.
Changing alignment should not be done lightly, because you aren’t just changing some behaviors or habits – you are revolting against cosmic forces and changing your destiny.
Alignment is generally more important at higher levels, since a bunch of low-level mooks have little effect on cosmic affairs. As a mechanic, alignment exists to say that “this person is aligned cosmically with x in a tangible way” for purposes of spells and magic items.
As one gets access to specific magics or has done things which have drawn the attention of extra planar beings, alignment matters both mechanically and for story purposes. At lower levels, detection and masking magic reveal or conceal those tangible connections to the cosmos. “Hide Alignment” isn’t going to keep someone from noticing whether you’re an obvious asshole or nice guy, but it will keep someone from seeing the tangible links you have to the greater conflict playing out across the planes. But until you’re a heavy, those tangible links will be relatively insignificant most of the time. But it’s those same links that explain why certain magic items work in certain ways for or against certain adversaries – they are attuned to the cosmic struggle in the same way everything else is; alignment is a wavelength, which also perhaps best explains the bizarre phenomenon which is alignment language.
Picking an alignment which fits your character’s personality and shaping the cosmos around those characters’ alignment choices is doing it backwards, which is why many people find alignment rules baffling. Unless you are actually using AD&D’s implied setting and cosmology, of course, there’s no mechanical reason to keep alignment. It becomes almost purely cosmetic since players and DMs use it mostly as a personality marker. It can be entirely discarded because it’s a rule that explains a character’s relationship to 1e AD&D’s batshit cosmology!
Please keep in mind, I’m not defending alignment as a mechanic, I’m trying to give context of WHY it’s not working the way people think it should.
The reason I like the 1 axis scale is that it’s a pretty simple range of “Is this character aligned with Mankind or aligned with Fae?”