I prefer 5e's approach with the classic 9, but it's just a descriptor no more or less important than any other.
But I've always viewed alignment as just helping me understand how a creature views the world. It's not a strightjacket, no one adheres to their alignment, people don't think in terms of alignment.
So someone that's lawful views the world as a clockwork mechanism and thinks laws and rules are important for a functioning society, although they may still disagree with specific laws. Someone that's chaotic doesn't think there's a natural order other than what we impose on it. Laws and structures may be useful as long as people still have freedom and, ideally, a voice in decisions.
So it can be useful, especially for NPCs and monster who are bit players. But I don't know or care what the alignment of my player's PCs are. For my own? It helps a bit as one aspect of their personality.