I will fully admit that the Alexandrian has left me with a visceral distaste for the term "disassociated mechanics."
I think a more broadly applicable way to communicate what Justin was getting at was synchronicity.
The divide between associated/disassociated mechanics is to me a question of how a given roleplaying game maintains a sense of immersion, the sense of completely losing yourself in the game.
And while a murky buzzword unto itself, I think immersion is a real thing, and I think the root of what it is is synchronicity.
Synchronicity I define as being a state where there is no difference between how a game feels, is described, and is perceived.
When you go to cast a Fireball, to use Justins example, synchronicity is achieved when how it feels to make that action, what it looks like when it occurs, and what the player perceives the other two as being are all the same thing.
And when one wants to get into the nitty gritty of how synchronicity is achieved,
that is where a whole bunch of buzzwordy words and phrases like dis/associated mechanics, clunkiness, fiddlyness, focused vs unfocused design, etc etc start cropping up.
And I think all of them to some degree or another are valuable, but the key thing is that synchronicity is only one part of the equation; it has to also be balanced with the intended experience of the game, its aesthetics if you will.
The right answers in a dungeon crawler like DND are not going to be the right ones for a game like Blades in the Dark, and neither games answers might actually apply to a wholly brand new game thats not quite like either one.
And important to note too that Immersion isn't a consequence of realism or any hullabaloo like that. Even the most gamey of games can be highly immersive.