I've bolded the part of your post that I find a bit contentious, though I don't think you meant it to be that!
Narrative in RPGing is closely related to
fiction. And just as there are different aspects to the fiction (as I've tried to bring out in some posts that were ultimately responses to something
@Sadras said), so I think there are analogously different ways of thinking about
narrative in a RPG.
How do we know that my warrior (to pick an example) is a whirlwind of death who sweeps across the battlefield, or a stalwart knightly type who can take down all comers? In AD&D that's all just in imagination with no connection to the mechanics - because 1 minute rounds and fairly simple but strict "engagement" rules mean that, in mechanical terms, it never comes out. Even in the stats of the game, there's no difference betrween AC 4 due to leather and 18 DEX or AC 4 due to mail and shield.
Whereas 4e definitely answers this question
through the fiction that results from application of the action declaration and resolution mechanics. We can tell if a warrior is moving or standing still; if a warrior is narrowly evading attack (AC bonus vs OAs) or deftly outwitting nearby enemies (shift that doesn't allow for OAs); if a warrior is a whirlwind of death (ranger twin-strike-y stuff) or a stalwart defender (fighter lockdown-y stuff).
This is why I don't see 4e's mechanical complexity as an
alternative to narrative. I see it as a tool for engaging the shared fiction of the situation and then producing a narrative via mechanical resolution processes. I would compare it, in that respect, to some elements of Rolemaster and many elements of Burning Wheel, and would contrast it with (say) classic D&D like Moldvay Basic and Gygax's AD&D, and with Tunnels & Trolls.
Absolutely agreed.
I find that the mechanics of the 4e AEDU Power matrix can express the fiction of those archetypes in ways I rarely experienced even in rules-heavy feat builds of Fighters in 3.5e, for example.
This is something I LOVE about 4e. I want to make it clear that as a D&D player, I've played 2e, 3e, 3.5e, 4e, and 5e, and 4e probably was the center of the most games I ran or played in, and I found it very suiting to my liking, and would happily play in that sandbox again if friends wanted to.
As someone who played 4e heavily, from 2008 all the way to 2014, I do have to say that I found certain mechanics of the game got to a point where they began to constrict the fiction rather than express it. If I wanted my character to do a theatrical action that I didn't have a power that could adequately express that action, I couldn't do it (or at least was highly encouraged not to do it, since I had consistently effective features I could do instead). The party didn't want me to do actions outside of my power choices because those would be subject to DM fiat rather than following the rules of my abilities, which were knowable and consistent enough. The chessgame actively discouraged inventive roleplaying within combat for that reason.
Utility powers were awesome! But so few were hard to judge. What is an encounter utility power if I'm using it outside of combat? The game seemed to be centered around the combat round, because they put so much effort into making it work so effectively, so very few of my class abilities were useful to draw upon in roleplaying moments like convincing the King or stopping a brawl. Honestly, I LOVED the new general abilities given to all Bards (not just Essentials Skalds) in Heroes of the Feywild precisely because they operated outside of the normal combat encounters.
Some of the best days in our 4e games, in my opinion, were ones we didn't roll initiative once. But I have party members who were NOT happy we never got to combat those sessions, because they were tricked out for combat and felt they didn't have the same functional, reliable tools they could draw upon in combat to tell their stories when we got to the outside of combat portions.
That's one reason I adore 5e so much. It carries over a lot of those ability flares, but there's never a passive pressure in the game suggesting, "if it's not in your power set, you can't do it." I feel emboldened by the game. So I understand when people say 4e felt videogamey – the powers passively suggest that there are limits to what you can attempt to do, even if that's not actually the case.
In Ocarina of Time, you can't jump unless you come to the edge of a cliff, but in Breath of the Wild, there is a dedicated Jump button, and boy, the things you can do once you can jump on command! But someone had to program that in there, and you still can't do EVERYTHING you might think of (I can't make Link wear a Goron Hardhat, for example). In D&D, you should be able to do just about anything you can imagine. But there are rules so that you don't get into a fight over whether you killed the goblin or not. The rules exist to empower the narrative and adjudicate and resolve issues where there's some uncertainty of success.
4e empowered the narrative, and empowered Players to be able to do really cool things without the DM saying, "nah, you failed at that." In earlier editions, a good DM may roll with the Players' ideas, or at least say "Yes, and." But a bad DM was nightmares to play with, because unless you're a spellcaster, you had no reliable way to do cool narrative things since the DM could just say you failed at that stunt. 4e evened the playing field with the powers, but in the process, many players felt that they could ONLY do the things they had powers for.
That, in my mind, is the root of 4e powers feeling "samey" – they may all do different things, but they feel like a gilded cage that is very hard to break out of. And the more powers that were added, the harder it was to narrative around, since the well-read DM might say that you can't do that because there's this other power that does that and you don't have that power. As the options increased (and options paralysis set in, mind you), the cage felt like it was closing in around us, rather than liberating us. And the Devs felt similarly – they felt they had to create powers for every different type of action you might take, and eventually it got to the point where there were narrative questions on why we couldn't just do everything on that list or why we could only do them a certain number of times. The pseudo-vancian nature of powers didn't really compute with the narrative they were trying to tell.
5e starts with a very different assumption, and I think it's a bit better for it. I do think martial characters struggle with toys, and I would personally suggest that all those martial characters should get martial adept powers and superiority dice. I don't want martial adept powers to become as widespread as everything under the sun. But I do want to see them empower that sort of tactical play that 4e had and give that level of narrative power back to martial character that want it. I'm of a mind to offer the feat free to any martial character (and offer something similar to casters to balance). But that's just my thoughts, and I'm starting to ramble a bit, so I'll end it there.