I'll accept alignment is useful when we get 70% interrater reliability on what Batman's alignment is.
People generally don't like having their actions labeled as evil by a peer, so there will continue to be alignment fights/squabbles, etc when not everyone uses the same shorthand. Like - why is poison specifically considered evil in a game of murder and looting?
When the game plays the same if no one writes an alignment on their sheet, it seems time to let the sacred cow be an optional rule or folded into ideals/traits/bonds/flaws. Putting a few personality traits in published material seems more helpful to new DM's than alignment is. It takes a little more space, but adds much more. If an NPC isn't worth a sentence or two on their traits, I don't think a 2 letter alignment will change that.