I think sometimes people forget that while role-playing games have role-playing, they are still games, people are trying to win and while this is often narrativly speaking (a personal win for glory, accomplishment, treasure or whatever) its also a mini win to pull of an action, roll the dice and succeed.
There's often this tension presented between Role Playing and Playing a Game, as if their exclusive choice, but both are really necessary to have an RPG, at all, yes. Systems support the 'game' side, but strong systems don't actually discourage the 'role' side, which comes more from the attitudes of the players & GM.
That said, when the depth of the game mechanics in a role-playing game gets too mathematical, it becomes too gamy pulling you too far out of the narrative element of the game
For the above reasons, I can't agree. Not that a system can't become clunky enough that re-calculating something in the middle of play can be distracting, just that throwing away the system isn't the only to avoid such distractions.
I think 3rd and 4th edition both suffered from that and if you used a lot of the extra rules in 2nd edition it did as well.
The thing is, all those additional options didn't just distract players from the game with their minutiae when handled at the wrong time, they also empowered players to create the character they wanted to play, and thus have more buy-in, investment, in the role/story side, as well.
3rd edition was fortunately more manageable because you could simply ignore many of the rules, they weren't core functions of the game. For example you could easily pull all the modifiers out of 3rd edition and use 5th edition adv./dis system
IIRC, 3e had over 20 named modifiers, and several variations on loosing your DEX bonus (flat-footed, flanked, etc) or having circumstantial bonuses or miss chances. Good luck pulling all those - you might as well try pulling the players' teeth! 4e at least brought it down to a few named modifiers, and Combat Advantage. Replacing CA with Advantage would be simple enough - it was binary like Adv (you either had it or didn't, multiple sources of CA didn't stack), but there was no corresponding Combat Disadvantage mechanic...
I think only 4th edition would be difficult to adjust since each power was basically its own mechanic, it was less flexible in that way.
Powers all used a specific format and set of jargon, so modding some aspect of them is theoretically simple - you just change the jargon definition of a keyword and all powers using that keyword are adjusted in that way. It's just that 4e was clear/gamey/functional enough that there wasn't a lot of impetus to modify it in the first place. It worked, why try to 'fix' it (even if you have an issue with how it worked).
That's where 5e's genius. By inserting DM rulings into the core resolution system, the precedent is set, and players are de-sensitized to 'house rules' or 'changes' - the DM's always making rulings anyway, so when he makes a blanket ruling - a 'house rule' however much it changes things - that's just par for the course. It's the way the classic game tended to be played because the classic game wasn't really designed from the ground up, but was more just exploring new ground, a trailblazer(npi). 5e is more evolved, but intentionally designed to evoke that quality.
In any case, I do think adv/dis system promotes role-playing and narrative/improvised actions by being a system designed for it.
Don't get me wrong, I like how adv/dis simplifies things, and makes basic tactics and actions like help clearly and significantly useful at the typical difficulties. But, it does
also discourage improv, tactics and teamwork, since once you're suffering from either advantage or disadvantage (or both), further adv/dis means nothing.
Players and GM's alike know what the interpretations will be mechanically
That's more true of the 'codified' sub-systems. You know that certain actions and abilities will have certain chances of certain effects, which encourages not just using them individually in a push-button fashion, but combining them in creative ways, or using them as a basis for something improvised. When players don't know what a given 'less codified' action might bring, they're more likely to go off what they know the DM is like than what they think might be a good idea, and that can get into some very 'meta' stuff, in its own right. Not that it's 'bad,' just that it's not the panacea it's made out to be, nor is having a good amount of 'codified' choices as bad as it's made out to be.
And I agree with his conclusion: because Advantage/Disadvantage is both fixed and non-stacking, I think it encourages colorful narrative rather than debate about realism and relative value, or attempts to find more modifiers to add. ("Wait...shouldn't I get +3 for swinging from the chandelier AND +1 for surprising him?"). Is it utterly revolutionary and redefines the genre? No.
In that sense, it's a continuation of Combat Advantage from 4e. Which is fine as far as it goes. Rolling an extra die isn't a new thing in 5e, either, 4e used the same mechanic for a whole range of things, mostly in the form of re-rolls, but the Avenger's OoE, for instance, worked exactly like the 5e Advantage that followed.
Where Advantage became interesting was with the addition of countervailing Disadvantage. You have two simple/universal modifiers, and they cancel. It does encourage whatever tactic or ability can get you advantage, which can be a colorful one-off thing on the player side. But once Adv/Dis is in play, you're done - stacking one or the other does nothing. So it's a bigger service to simplifying combat than to making it more colorful (which you can still do, but you could always do).
But philosophically and in practice my experience has been that it results in a different "feel" at the table. It's not like the switching from THAC0 to positive ACs, which is purely a reframing of terms; it's both a deeper and more subtle change than that.
It does. I suppose it's more noticeable when returning to the hobby or having stuck with the classic game until now. Going from AD&D to 3e to 4e to 5e the evolution leading to Adv/Dis is much clearer, and feels less dramatic.