Gantros
Explorer
Another point is that D&D has always had dissociated mechanics/play:
1. Choosing a PC's race
2. Hit points
3. Saving throws
4. Xp for gold
5. Certain classes being banned from wearing particular types of armour or weapons
6. Handwaving the boring bits - travelling to the dungeon, shopping for equipment
7. Use of reported speech
8. Starting a PC's career on completion of his 1st level training rather than from birth
Just wanted to point out that none of these are examples of dissociated mechanics, as defined in the Alexandrian essay.
#1, 6, 7 & 8 are examples of metagaming, in which out-of-game information or resources (such as player's knowledge of the pros & cons of various races, or DM's knowledge of when interesting events will and will not happen in the game world) are used to affect in-game decisions. It's a bit of a stretch to call these "mechanics" at all, since they really represent different ways of using various rules rather than actual rules themselves.
The rest are examples of abstracted mechanics, in which a range of various factors and circumstances are rolled up into a simplified numerical value for the sake of convenience. HP and Saving Throws each represent a character's ability to avoid serious harm or death through a combination of skill, experience, natural ability, luck, fate, divine favor, magical assistance, etc. XP for gold made the assumption that adventurers who amassed large amount of wealth had faced and overcome many difficult challenges to do so. Armor and weapon restrictions assumed some combination of cultural and practical factors.
All of the above mechanics still have a direct association with specific behaviors and outcomes in the game world. Take HP for example. It is directly affected by a character's experience level, class, and ability scores, all of which are things an avatar would have some awareness of. It also degrades as a character absorbs blows, gets tired, or presses their luck repeatedly - again all things the character could feel and understand. So when a player uses HP to make informed decisions about when to flee or continue fighting, or whether or not to jump off a 20' cliff, we can easily envision the character making the same decision based on the same set of information.
Contrast this with 4e daily powers, which dissociate the mechanic (i.e. how often you can use the power) from any meaningful factors or circumstances a character would conceivably be aware of or able to influence in the game world (such as skill level, experience, fatigue, luck, or prior preparation). The mechanic allows the player to make informed decisions about when to use it, but provides no explanation of how the character would arrive at the same conclusion.
Also I don't think it was being asserted that 3e and earlier editions were free of dissociated mechanics, but rather that in 4e they appear much more frequently and so are a bigger problem for those that find them undesirable.