I'm uncertain this is true. There were a bunch of different ways to trip in 2e. The cleanest was standard to-hit roll followed by the defender rolling a d20 vs. Dexterity with modifiers for moving and awareness. It is quite difficult to compare the efficiency of the subsystems in 2e and 4e.
Where there. I remember it seemed like a new thing in 3e. Then again, I skipped C&T. Maybe it was in there. I've heard a lot of 3e-isms were.
In any case 'just as good' is hard to quantify across systems. 2e (pre-C&T, say) and 4e would both have used some sort of improvised mechanic to trip, plus 4e had powers that knocked prone. 3e had very specific rules on tripping and being better at tripping (and they led to some rather outre builds that did some rather silly things in combat). You could tell that a character with Improved Trip in 3e or a power that made targets prone in 4e was 'better' at tripping than one without, but across game? Is the 3e fighter better because he can Trip every attack of every round? Is the 4e character better because he can knock a flying dragon prone?
See above. Dissociation removes that agency to try anything, because it throws arbitrary restrictions on what the character can do. That said, I'm glad you've found the definition to be novel.
That is indeed, an atypical definition. Placing restrictions on what a character can do is dissociative? So Vancian magic systems are dissociative? Or are they merely in violation of this central tenet in a different way?
Exactly right. Certainly better than "you can't do that because the rules say you can't."
The rules say you can't do a lot of things. They're rules. 3e trained-only skills? There are things you can't do. AD&D weapon & armor proscriptions? Things you can't do. Vancian magic? Clerical healing niche protection? 3e 'Trapfinding.'
Are you advocating for something like the old MSH, where spiderman /might/ lift Mt. Everest, 'some of the time?' with enough shifts?
I actually agree with the sentiment to a small degree: rules are better when they define what you can do, rather than what you can't (and it can be tricky assuring that the former doesn't imply the latter). Expanding or open-ended skill lists, for instance, suffer terribly from creating incompetence in characters who lack a given skill. 4e using a short, fixed skill list and simply dividing up all tasks among those skills, or 5e dividing all tasks among 6 stats are examples of avoiding that. (OTOH, 13A open-ended backgrounds and 5e open-to-expansion proficiencies tend the other way a bit.) Hero's another great example of both. It's effects-based powers system leaves the game wide open to characters doing anything the player can imagine, while it's long skill list and several open-ended skills make broadly-skilled characters problematic, and leave other characters with unexpected blind spots ("But, I'm a scientist, I have 14- physics" "Ah, but you don't have KS: Scalar Field Dark Matter!"). In 4e, the infamous p42, leaves an out that prevents powers from defining what you can't do. So you end up with things you definitively /can/ do (powers, feats, features, skills) - and things you can't /definitively/ do, but might be able to attempt (p42).
In practice, IMX, most players are happy enough with the range and number of things a 4e character definitively /can/ do to be disappointed in the things he can't /definitively/ do. Those that aren't stretch things - either with the formal process in p42, or by telling the DM what they're trying, requiring some sort of ruling, just as D&D has always done (just not nearly as often, and not for basic things characters try all the time).