Thinking as a character rather than trying to conform to rigid alignment standards makes so much more sense. In real life, people's alignment may vary from issue to issue thanks to cognitive dissonance or just nuanced views. The more restrictive one is, the more potential there is for frustration or annoyance or sheer disagreement on the part of the player. It's not constructive or fun for players to think about how they disagree with the developers rather than being drawn into the game world.
I don't play games with brain eating squid men and psychic neanderthals who ride dragons looking for a mirror of reality. Yeah, in the real world eeevol doesn't exist. Chose an evil actor in the world of politics and chances are they would tell you their actions are actually good -- they are carrying out the commands of god, protecting the people of their nation or their people, ensuring stability in the region . . .
But to hades with the real world, it kinda sucks.
In this world two sisters, light and dark, were in perfect harmony until the light sister decided to create the sun and bring life to the world. Shar's sister betrayed her and she has waged an eons old battle to right this ancient wrong, to destroy all life on earth and to return the world to perfect, perpetual darkness. Shar, the god of darkness, became the first evil from which all other evil was born those who follows her do so for their own reasons but Shar's aims are evil, her powers are evil and her followers further that evil or lose their powers.
Sure there is "sheer disagreement on the part of the player" but that's part of the fun. People like to debate D&D rules, if they didn't care they wouldn't be motivated to debate. Larian has already made its own world without alignment but they put that side to play in Faerun. And people are going to be annoyed if you don't have alignment -- when 4th edition removed alignment from the game people were furious.
Again, without alignment it's not D&D. Sure, I'd play a Westeros game where motivations mirrored the real world. But D&D was based on Tolkein and Moorcock and alignment matters in those worlds and in Faerun. Take good and evil out of Tolkein and you've lost the story. Eliminate Law and Chaos from Elric's world and nothing makes sense. Take alignment out of Faerun and . . .
