"Good animation" isn't gimmicky to me (what a dialectic trick you tried there). "Gimmicky" is making up flashy effects that AREN'T a synonym of good animation nor the only way to achieve it (you have examples of good animation in this very fight that doesn't need blurry auras and hyperbolic outcomes to look dynamic) and were never to be seen in the original content and, therefore, the style Oda is applying to his actions.
Why does it matter the style Oda is applying to his action?
Oda has no sway on how the anime executes his action more broadly, and I think the anime pretty much kept the same intent for what Onigiri is supposed to be, a charge attack that causes collateral damage.
Each work has its own style and tone; the execution itself is dependant on it. If I'm adapting to film a novel by a naturalistic author and I feel like adding a strong thunder effect after a character burst into fury It will be laughable because the naturalistic style of the whole story doesn't accept for obvious reasons such melodramatic resources no matter how "cinematographic" they can be. In a similar fashion, the moment Oda's work isn't prone to surrouding each character with a burst of aura or depicting an attack like it is a nuclear bomb that comes with all kind of additional bursts, the moment the ADAPTATION will need to avoid resources that clearly don't fit the original style. If not, the anime ends up looking like a naturalistic story with effects from a soap opera, which is what kinds of happen here. And you may like a naturalistic novel adapted with thunder effects, dramatic zooms and so on to "increase the tension of the scene" but it doesn't make it better because, at the end of the day, there's an incongruency between the original material and the resources used to animate it.
Your argument here doesn't make a lick of sense when you think about how your applying to the Zoro scene, nor does it effectively follow on at all.
Oda is irrelevant in terms of how the action is translated to animation, and the action sequence in question did not at all violate the tone and style of the series, which is an over the top melodramatic action shonen.
In terms of how they adapt the manga, the anime staff don't need to avoid anything in their potrayal of it. They are free to animate or draw the characters how they please(and considering that One Piece is such a ludicrously over the top series, that gives them plenty of stylistic wiggle room).
The anime is not bound by a need to replicate Oda's style(even though it feels compelled to do so anyway).
You say that its incongruent for these things to happen in One Piece, but don't really explain how or why its tonally out of place, instead falling back on "it didn't happen in the manga."
The anime's job is not to replicate the manga, its to be an action shonen anime(which One Piece is), and action shonen anime have ridiculous over the top fight scenes(which One Piece does).
Considering the actual anime additions to the fight,(ie, Killer leaping back, throwing flying slashes before Zoro charges at him, which prompts killer to charge back), whats actually shown is perfectly in line with the tone of the series and the intent of the scene(which is solely to generate hype).
I understand perfectly how adaptions work. I may be moronic, but at least I understand that animation isn't all about flashy auras, strident sound effects, overdramatic lightning and so on. Do you even get what I'm criticizing here? Because it is quite annoying how you reduce it to "animation resources" even though there are huge differences between each resource you may apply to animate a scene and I'm discussing just some of them.
I understand perfectly what your saying, I'm just saying your example is completely moronic.
Your point is its tonally dissonant for One Piece to be animated in an over the top and flashy way because over the top flashy animation doesn't exist in that fashion in the original source material.
And I think thats honestly an absolutely moronic point. Like, hitting your head against a wall till you get brain damage levels of dumb. I had to calm myself down after digesting just how laughable that point was. This is me being very tame and straightforward.
I've had to rewrite this multiple times not to mock how moronic that point is. Your core example is just not applicable to One Piece. I know your using this to demonstrate tone dissonance, but it just doesn't work at all for your point here.
One Piece is, an over the top, overly melodramatic shonen, with ridiculous fight sequences. Your analogy of a naturalistic work with soap opera elements does not hold up as a comparison even under the slightest scrutiny.
It is not tonally dissonant, or destroying the immersion of reality in the series, to animate those fight scenes in an over the top fashion. If anything, the series perfectly lends itself exactly to that kind of action.
In terms of story elements and potrayal, the anime is not inherently bound to Oda, and can take creative liberties with how some of the characters abilities are shown. Zoro for example, is someone that is frequently shown to have an aura around him, and that has been highlighted well in other forms of media like movies and specials.
I'm not really taken out of the action(based on actually watching the show) by the fact that Zoro, a guy who has an aura, and is shown with one frequently across multiple pieces media, has an aura.
As for following Oda's action, Oda's style is irrelevant to how animators interpret his action. Oda's manga is not a guide for animators about how they should handle his action. Considering how loose on details Oda is with his action, they are at most a blueprint.
I think of movies like 6 and 9 with how they each had crazy takes on portraying and animators Luffy's abilities. This example comes to mind for me.
You don't have creative freedom when adapting unless you want to turn a naturalistic story into a soap opera (again, allow me to keep this example which, albeit exagerated, perfectly represents the problem with freedom when adapting something that doesn't belong to you).
Um. This is just incorrect. You have all the creative freedom in the world when adapting something. Your example does a horrific job of representing the problem, because the problem your example is supposed to represent doesn't actually at all fit with this scenario. Like, even remotely.
I don't even get why people are so hung about it. The point of the scene was to convey that Luffy was angry and by hype. Zoro defeating Killer was supposed to be a hype moment. As long as both those scenes could generate that response, they succeeded(and I would say both of them did).
Colour and animation can be used in a lot of ways. The problem here is whether an usage is actually justified by the original material you are adapting; here it isn't. A simple animation in which the accelerated punch finally hits Kaido, and then the action slightly slows down and everything goes silent except for the sound of the dragon's head receiving the impact only for it to re-accelerate abruptly for the dragon being sent to the ground, would be way more faithful to the original material and still an exercise of animation.
The original material isn't really that relevant in terms of how its animated. Hell, faithfulness, in of itself, does not make an adaptation good or better.
A good example of what I mean by this is the DIO fight with Jotaro in the 90's JoJo's OVA vs the DIO fight with Jotaro in the David production anime. The David production anime is significantly more faithful to the source material and tone of the original source material, but its still vastly inferior to the 90's OVA's version of that. Its not as well animated, its not as well directed, its not as tense, the tone of the OVA(though different from the manga) is far better actualized than the anime, and even though things in the OVA are changed from the manga, those additions and changes, although departures, actually make the fight more enjoyable, again, even if it is tonally dissonant to the manga.
The point of the scene in the manga was to highlight Luffy's anger and also generate hype for Luffy fighting Kaido. There is no issue with the anime's interpretation of that scene, with the animation perfectly articulating Luffy's anger, as well as generating hype for the scene through the swelling of a triumphant and climatic OST.
One Piece may exaggerate movements in a way that feels organic for the character or movement depicted following its cartoonish style; this has nothing to do with Sabo waving his fist without a logic in the context of his attack, being only made this way because the animator obviously likes to recreate himself unnecessarily by animating inorganic movements like it. Basically, many of his characters look like they're dancing at some point.
There was a very clear reason why Sabo was waving his fists, its called anticipation.
In saying that, I will say that my thoughts around that particular animator is pretty nuanced, with my main problem, not necessarily coming so much with how he makes limbs really wavy(that can be effective for building anticipation), but more around how he handles camera movement and impact.
I believe an animator way back called out how Naotoshi Shida used camera movement during his action cuts, noting that by having the camera move so much, the impact in scenes can be significantly reduced. This is particularly problematic for action sequences(I only have two sources left, but I think they demonstrate my point).
Shida has a few problems. First is that the camera is moving so much in some of his cuts its hard to follow exactly what's happening during the cut.
For example, in this Doffy scene, you miss Doffy's clone getting kicked away by Luffy, Doffy apparently attacking Luffy as the clone is getting kicked away, and Doffy's leg hardening. Everything happens so quick that stuff is lost in translation that makes the scene a bit awkward to follow in some instances.
Second, due to the camera moving so much in some of his cuts the impact within those scenes tend to be significantly reduced.
This isn't exactly from One Piece, but the example holds true for that Doffy scene as well. After the initial clash, the camera rests on Goku for a bit, however, the impact of the action afterwards is ruined by the fact the camera doesn't stop moving, and doesn't give time for the audience to process the impact of a scene before pulling away.
I think while something like Zoro's scene this episode also had a lot of camera movement, there is a very clear difference in impact, with the camera not just constantly moving because it can, but moving to properly trail the characters actions, with the camera actually stopping in key moments, to allow the impact of a scene to set in. When Zoro finally lands the onigiri, it changes camera angles a few time, but the camera isn't overly animated during those scenes.
These problems tend to meld together.
I don't think the waviness of limbs and stuff is necessarily a terrible thing(particularly his method of doing it), though it definitely isn't exactly my personal cup of tea.