Nagol, I appreciate the lengthy post. I hope this one doesn't come across as snarky.
So to use your example of modelling Come and Get It in Champions: Are you telling me that:
I cannot model Come and Get It in Champions in a way that I find adequately connected to the game world when I play with my friends in my group?
Yeah, pretty much.
I mean take a look a the power: it is equally effective against a human fighter, a 6,000 lb dragon, a mindless and spell-immune golem, and a wizard whose only ability is to throw lightning bolts and is pathologically afraid of melee combat. It involves no ability inherent to the character since it is drawing opponents from beyond his ability to reach into striking range. It is based on puissant skill at arms and combat training and takes effect depending only on opponents being visible.
The only way to get that flexibility is disassociate the ability from the game world and apply rationales as to why it happened this time. It isn't an ability the character can draw upon; it a situation the player can engineer.
Imagine the scene, the fighter is being set upon by a small group of mooks -- a mixture of thugs, zombies, and longbowmen. "If only they came at me as a wave, I can take them quickly!" And then it happens. So what did the character do to get all three types to rush him? Wave at them? Unlikely to sway the zombies. Taunt them with "Try my steel"? Unlikely to sway the longbowmen or zombies. Feign weakness and draw them in? Unlikely to sway the longbowmen. a more likely reason can be created by using the opponent's motivations and tactical failure, but that's outside the character.
I can't see how you possibly justify such an assertion. And without justifying that assertion you can not say that the Champions version of Come and Get It is objectively disocciated. It must be subjective.
Given that, using your example, which of these tells us something:
a) Champions Come and Get is disocciated
b) I couldn't figure out whether Champions Come and Get it should be charisma-based, or intelligence based or something else
What information is associated and disocciated telling me? It tells me nothing that your example - without the use of the words associated and disocciated - tells me.
What it does do is provide the ongoing basis for believing (incorrectly) that the mechanic is the problem, rather than the mismatch between your priorities and preferences (which you stated quite honestly - kudos) and the mechanic.
Since I don't share those preferences I don't have the problem.
Can you now see how the concept of disocciation goes nowhere?
The mechanical mismatch between my priorities and disassociated mechanics is the problem. There's nothing inherently wrong with them. I just prefer to run my character without relying on them and will continue to prefer game systems where such mechanics are kept away from me -- especially when I'm engaged with the game world as opposed to bookkeeping.
Disassociated mechanics are at their best when they are being used to control outcomes in keeping with genre or table preferences that would directly contradict characterisation (for example, adding a complication to a rescue scene). They can be quite decent tools for shared world-building/shared narrative construction as well like -- Strands of Fate Declarations.
The concept of disassociation does go somewhere. It helps me categorise RPGs in a way that is conducive for me to find a game I'd like to run and/or play and to explain to others why I like chocolate, but don't like strawberry.