I found it really useful in 3e when I houseruled it to be supernatural forces divorced from morality, with a lot of aligned outsiders, holy weapons, aligned spells, and paladin detect and smite evil. I had most mortals neutral unless they had a supernatural connection to supernatural forces (an aligned god, aligned outsider aspect, whatever). It was then a lot more like ritual purity aspects and cosmic forces which felt cool in ways to engage with mechanically and narratively.
5e has very little mechanical engagement with alignment, a few magic items in the DMG is what I mostly recall. It is a descriptor in new D&D monsters that I generally expect, but do not feel a big need for.
For 5e it has mostly been useful in seeing how some classic stuff has changed, like the portrayal of orcs across 5e going from more inherently and divinely evil in the 5e MM and Volo's than in past editions, to not evil in recent write ups without a lot of narrative descriptions of changes.