I like alignment because:
1) It expresses the cosmological nature of the Planescape / Great Wheel cosmology which I love.
2) It is indispensable to me as a DM, and much easier to use than any alternative.
3) It feels very D&D-y, and I like my D&D to be very D&D-y, and my other role-playing games to be not-D&D-y.
Notes on how I use alignment:
-I don't like major alignment based mechanical restrictions. Monks have to be lawful; barbarians can't be, etc. What I would do, is if a devotion paladin is consistently role-played as committed to duty and order, but isn't noticeably more altruistic than the average person, I wouldn't take away their paladin powers, but I might switch them to oath of the crown to fit their actual role-play. The multiverse knows what your alignment is so I'm fine with magic being able to interact with that. I'm also fine with 5e's version of most mortal magic not really being able to detect alignment.
-I rely on 3e's definitions of what the alignment elements (good, evil, neutrality (GvE), law, chaos, neutrality (LvC)) and the nine alignments mean. Edition is key here. 3e's definitions are far and away the best ever published for the game. I often think that many people who don't like alignment are using the inferior definitions from other editions, so we aren't really even talking about the same thing. If Gary Gygax were still alive, I'd debate him on how 3e alignment is better than his original 1e, and I think I might have a chance of convincing him.
-Alignment is a better method of giving a DM useful D&D relevant role-playing guidance about NPCs and cultures you may come across than any other system I've seen. LE, NE, and CE are distinctly different.
When Van Richten's Guide to Ravenloft left out alignment, it made it harder to interpret the motivations and methods of the monsters they put in there. Yeah, I could see something was clearly evil, but what was its approach likely to be? Without alignment it put more strain on me as the DM to have to figure that stuff out. With alignment, I'd know at a glance.
This is also the major practical reason I immensely dislike removing alignments from humanoids (redefining humanoid as essentially refering to bipedal creatures with human-identical psychology). When I first ran into the harengon, without alignment I didn't have a baseline to understand their culture. Okay, so they can be any alignment. But the NPCs you are running into happen to be CE. This gives me very little to work with to have an idea of their society. (I eventually decided their society was probably CN.)
Knowing that dwarves tend strongly towards Law and mildly towards Good, and that elves tend strongly towards both Chaos and Good immediately tells me actionable info as a DM that is frustrating when it isn't there.
-I have also assumed that individuals can vary, and tendencies are just that. We've always assumed that goblins, orcs, dwarves, and elves are all people (albeit, alien people, not humans) and that they aren't all the same, and it isn't morally justifiable to kill an alien person just because there is a tendency towards evil attitudes and behaviors amongst them as a whole. I don't know why anyone can't get this. It seems so obvious, but it seems like there is some sort of way of seeing things needed that isn't doable for everyone.
-The perfect is the enemy of the good. Most objections to the use of alignment as unrealistic or coming from faulty premises, etc, are failing to realize that it's good enough for D&D usage. Heck, I think of friends and family members in real life in terms of alignment sometimes! Does it fully express their individuality? Of course not. Is it accurate enough that it could be used for legitimate predictive ability? Absolutely! Lots of people take "alignment quizzes" and feel like the answers fit them pretty well. So the objects that since it isn't perfect we shouldn't use it, are not at all persuasive to me. Telling me Baron So and So is LE and Duchess Such and Such is CN immediately give me useful information if they suddenly need to be on the scene and I haven't had time to study their backstories. Telling me goblins tend towards NE immediately gives me an idea of how a randomly rolled group of 5 goblins in a forest is likely to interact with an adventuring party. (All I need to do is decide in real broad terms "Why are they here?" and unless I want to specifically make them unusual, that's enough to role-play interactions. Spoiler: They probably aren't going to attack, and are likely to converse and then go their own way if the party isn't obviously aggressive.)
-Other than occasional magical stuff, alignment is less important for PCs than for NPCs. I tell players that if they significantly deviate from their written alignment, it might end up changing in my notes, and ask if they want to be told if that happens. The only likely consequence is what plane they end up at when they die and/or how a worshiped deity might react to them. And this might come up!