One of the things people like about Good and Evil is that it provides a space for a supernatural (maybe meta-natural) conflict between deities that personify these extremes and the world in which we play our games is a battleground for these forces. In general this is a potentially fun conceit to work with, giving you people with varying dedication to these divine forces and fulfilling their roles as champions of their divinity. All potentially awesome.
But, in addition to the problems alluded to earlier, there is practical trouble with this particular dichotomy: while many say that there needs to be a balance (and there does, practically, need to be a balance in order for this battle to work since otherwise there might be a winner), it’s perfectly clear that there is absolutely no need nor desire for a balance between Good and Evil. Any rational being would want a world of Good, full stop. So where would allies of Evil even come from? Who would want that shit?
Originally this was not the driving dichotomy in D&D. It was originally Moorcockian, an hilarious word I have just invented. In Moorcock’s Eternal Champion series (of which the Elric stories are just one facet) the divine dichotomy is between Law and Chaos. Now this is where it’s at: if you want a divine dichotomy, this is one you can work with.
First, there is no moral bias here. You can have good people on both sides. You can have awful people on both sides. In order to exploit the dichotomy for story purposes you don’t have to simplify anyone’s position and you don’t have to suppose that free-thinking individuals would credibly desire a world in which it was ordinary to get murdered.
More usefully, we can imagine people who would desire the extremes of course — perfect Law were everything is ordered and predictable and safe or perfect Chaos where individual desires reign and things are constantly new and unsafe but exciting. But we can also see that the middle ground, a balance, is in fact genuinely desirable. You don’t have to cart out the obviously specious claim that “good can’t exist without evil” and therefore that evil is somehow necessary. Even if Good has no interesting definition without the contrast of evil, that’s just fine! It’s still Good!
But Law and Chaos genuinely stress against each other in a fun fashion. Pushing more towards one has amusing possibilities for story without forcing a particular morality on anyone. And the gods themselves can be interesting now! Gods of Evil are inexplicable elemental things that make no intrinsic sense since they have no believable agenda. But Law and Chaos do! These are gods you definitely want to have a chat with. An audience with an Evil god is not going to go well. An audience with a Good god is going to be dull since their position is obviously good (it’s even called that). But an audience with a god of Law or Chaos, well that’s going to be interesting. It has no obvious arc. And their agenda is credible and either could be persuasive. But ultimately most people are going to want a little from column A and a little from column B.
I think the underlying concept of alignment is a compelling setting choice. That doesn’t mean every setting should have it, but it’s a choice that makes some sense. It makes a particular kind of world that’s fun to play games in. It’s the moral alignment that makes no sense and creates a dull (and, ultimately, racist and stupid) world. One agenda is obvious and the other is not credible. You can’t help but fight cardboard cut-out enemies since if you argued with the Evil ones you would have to conclude that they were either automata or insane.
If you imagine a plane of each extreme, a plane of Good and a plane of Evil, you find that the Good place is paralyzingly boring and the Evil place is perfectly undesirable (and unsustainable — the Evil places imagined in D&D have absolutely necessary non-Evil behaviour in order to persist: they cannot be “perfect” representations of Evil because Evil doesn’t function). But if you imagine a perfect plane of Law and a perfect place of Chaos you can imagine interesting (however undesirable) places where interaction still makes sense. You’re not murdered as soon as you show up and you still have something fun to do, beating down both Good and Evil planes for playability.
So it’s not alignment that a rail against (though I have little use for it, it’s because it’s just not a setting conceit in my games — don’t need a divine presence of this kind) but the insistence on using it for a moral dichotomy. A moral dichotomy is not a choice because one side is obviously, perfectly, inarguably, better. How’s that a fun way to run a universe?