How the Game has Changed

Alignment
The World's Most Popular fantasy role-playing game is now in its 5 edition, and has been for some time. A lot has changed since the very first version of the game was released in 1974, an event which inaugurated the entire role-playing hobby and has had numerous peripheral effects over the decades on popular culture. Several aspects of today's game differ from previous editions, perhaps none more than the way alignment is treated.

The original edition, my copy came in a white box containing three little brown books, listed three alignment choices. Like with many aspects of the early game, there was very little in terms of explanation of concepts such as alignment in those three little brown books. Volume I simply stated, "Before the game begins it is not only necessary to select a role, but it is also necessary to determine what stance the character will take - Law, Neutrality, or Chaos." There followed a table of creatures arranged according to their alignment, some creatures being listed under more than one implying that some individuals may align differently within the same creature type. For example, dragons appear under Neutrality and also under Chaos, implying that individual dragons may side with the Neutrality forces or with the forces of Chaos - perhaps even changing from one side to another depending on circumstances.
Later editions of the game added another dimension, that of Good and Evil such that Lawful Good, Lawful Evil, Chaotic Good, Chaotic Evil and combinations of each with Neutrality all become possible alignments. As other non-D&D systems are designed, many leave alignment aside. The alignment concept then becomes linked to character/creature personality once ideas of good and evil behavior is added in. Eventually, character alignment is seen as a sort of role-playing straight-jacket by some as referees attempt to enforce characters acting according to their alignment.
The 5th edition seems to remove much of the importance of alignment, although the term is retained.(perhaps in order to make 5e seem more connected to editions of old?) For example, traditional class restrictions, such as the requirement for paladins to be Lawful Good, are dropped altogether and a 5e paladin may be of any alignment.
As referee of my own campaign I prefer the original three alignments. Good and evil are moral judgments and seem best left to each player to role-play their character as they see fit. Disputes over the morality of certain character actions can make for good role-playing. In contrast, Law and Chaos are more objective driven and can work quite well as ideologically motivated opposing sides in a conflict, rather similar to capitalism and communism during the cold war era. A more direct literary comparison might be the free peoples and the forces of shadow.
It all comes down to what you want out of your game. Factions in conflict are a desirable thing to have in a game setting and that is just how I like to use alignment in my games. The original three alignment system gives players the option to form an alliance, negotiate a truce, even to potentially convert certain individuals to your way of thinking - all good reasons to role-play! While many things  about the game have improved over the decades since 1974, alignment may not be one of them.