Can you explain a bit more about what is useful for world-building and npc design? As in it's one thing to have in mind a particular kind of character or kingdom/society and then think about whether it's lawful, neutral, or chaotic, but in those cases the worldbuilding part is already done and you are just applying labels. In the other threads people were saying alignment is useful as a short hand when you don't have time to think, but when you are siting down and thinking about a specific society in your world or a specific character and their motivations within the context of your setting, what added value does alignment provide?
Unless alignment is treated as metaphysical, in which case you get things like this (from the Rules Cyclopedia):
"A character may not learn a different alignment language unless he changes alignments. In such a case, the character forgets the old alignment language and starts using the new one immediately."
I actually love that because it's so weird. If I was going to use alignment to build a kingdom everyone would only speak in alignment all the time. Lawful would have no regional dialects.