In my opinion, both Oda and the readers made some mistakes regarding Gear Fifth.
First and foremost, the readers have been taking a wrong approach to it because of the whole "god" label. Most if not all users here have been probably raised in a culture more or less influenced by Abrahamic myths where deities are all mighty, but Nika has been portrayed like a tulpa-like entity, in my opinion; this also fits recent statements on devil fruit origin by Vegapunk. I think readers may have gotten defensive against "Sun God Nika" because they understand "god" as an extremely powerful entity by default and assume it diminishes the supposed weakness of the Gomu Gomu as a fruit, but for all we know Nika's divinity may have nothing to do with anything powerful. Personally, I don't see any significant difference between the Nika model and what I expected from the Gomu Gomu awakening. I'm not sure to what extent Oda sees the change as a sublimation of a previously average power instead of just a renaming to magnify the bigger picture of his story; proof is that he had already referred to the Gomu Gomu as a ridiculous power in an SBS, if I recall correctly.
It's also the readers's fault that they don't want One Piece to be how it's supposed to. Let's face it, manga and anime fans aren't usually the most mature and cultured out there and what's mainly popular among them, especially shonen fans, are edgier approaches; if you doubt it, try counting how many AMVs so far have used that Bring me to life song from Evanescence, it's crazy. One Piece does something quite unique as a piece of work which in my opinion sets it apart, and that's the focus on joy and laughter. Authors tend to seek depth in sorrow, suffering, darkness —but very few can craft their work around happiness, yet that's exactly what One Piece is: characters with distinctive laughs, a main character based on a kid who's the new Joy Boy, the Pirate King laughing at the most mysterious treasure and Laugh Tale as final destination. Not only that, but the core themes fit perfectly and the combination of laughter, joy, bouncing, freedom... It's an incredibly warming and funny reading once you get past the "edgy teenage" phase and it's pretty clear Oda wanted to take that feeling back, a feeling that was lost for quite a while in my perspective, with a cartoonish Gear that, funnily enough, remind us of the rubber hose style.
But I don't think Oda did it well enough. Part of why the readers reacted negatively to Gear Fifth and the Nika reveal was how superficially the author prepared the scenario. The name "Nika" wasn't a thing until Who's Who, Who's Who himself wasn't a thing until Onigashima (in spite of linking to CP9) and no serious doubt about the Gomu Gomu's true nature had been truly built in the reader. Connecting small things better (e.g. turning that unnamed CP9 agent during Ohara into young Who's Who), making a more explicit usage of the "nika" smirk (e.g. having important people using it in their significant moments; Oda vaguely did something similar since, for example, Roger smirks a "niya" during his execution, but that's not exactly "nika"); putting more focus on the importance of the Gomu Gomu (wasn't treated nor remarked as anything special until its awakening); stressing Kaidou as a failed Joy Boy who fell into depression (which is more or less what his character is about, but since Oda didn't work it enough many found out of place that Kaidou's fight turned into a "Having fun?" dynamic even though it made total sense); etc.
It's obvious Oda has some main themes more or less thought of; it's no coincidence that "don" (which people like Tom defended) sounds like "dawn" and is the sound drums make (e.g. during the Skypiea party), or how the sun is a symbol used by pretty much every oppresed people in this story, is directly related to freedom (Sun Pirates) and revered by the Shandians and Elbaf giants, or how the yet-to-be-explained quote by this Willie Gallon guy (which Oda put in a chapter with no apparent reason) totally sounds like Vegapunk's explanation on how devil fruit came to exist. Just too many of these themes perfectly fit the figure of Joyboy from real African folklore and it seems obvious Oda made some research on it to build the foundations of his work.
So, to summarize, could Gear Fifth plus Nika have been handled better? I think so. Is it a good idea still? I think so too.
First and foremost, the readers have been taking a wrong approach to it because of the whole "god" label. Most if not all users here have been probably raised in a culture more or less influenced by Abrahamic myths where deities are all mighty, but Nika has been portrayed like a tulpa-like entity, in my opinion; this also fits recent statements on devil fruit origin by Vegapunk. I think readers may have gotten defensive against "Sun God Nika" because they understand "god" as an extremely powerful entity by default and assume it diminishes the supposed weakness of the Gomu Gomu as a fruit, but for all we know Nika's divinity may have nothing to do with anything powerful. Personally, I don't see any significant difference between the Nika model and what I expected from the Gomu Gomu awakening. I'm not sure to what extent Oda sees the change as a sublimation of a previously average power instead of just a renaming to magnify the bigger picture of his story; proof is that he had already referred to the Gomu Gomu as a ridiculous power in an SBS, if I recall correctly.
It's also the readers's fault that they don't want One Piece to be how it's supposed to. Let's face it, manga and anime fans aren't usually the most mature and cultured out there and what's mainly popular among them, especially shonen fans, are edgier approaches; if you doubt it, try counting how many AMVs so far have used that Bring me to life song from Evanescence, it's crazy. One Piece does something quite unique as a piece of work which in my opinion sets it apart, and that's the focus on joy and laughter. Authors tend to seek depth in sorrow, suffering, darkness —but very few can craft their work around happiness, yet that's exactly what One Piece is: characters with distinctive laughs, a main character based on a kid who's the new Joy Boy, the Pirate King laughing at the most mysterious treasure and Laugh Tale as final destination. Not only that, but the core themes fit perfectly and the combination of laughter, joy, bouncing, freedom... It's an incredibly warming and funny reading once you get past the "edgy teenage" phase and it's pretty clear Oda wanted to take that feeling back, a feeling that was lost for quite a while in my perspective, with a cartoonish Gear that, funnily enough, remind us of the rubber hose style.
But I don't think Oda did it well enough. Part of why the readers reacted negatively to Gear Fifth and the Nika reveal was how superficially the author prepared the scenario. The name "Nika" wasn't a thing until Who's Who, Who's Who himself wasn't a thing until Onigashima (in spite of linking to CP9) and no serious doubt about the Gomu Gomu's true nature had been truly built in the reader. Connecting small things better (e.g. turning that unnamed CP9 agent during Ohara into young Who's Who), making a more explicit usage of the "nika" smirk (e.g. having important people using it in their significant moments; Oda vaguely did something similar since, for example, Roger smirks a "niya" during his execution, but that's not exactly "nika"); putting more focus on the importance of the Gomu Gomu (wasn't treated nor remarked as anything special until its awakening); stressing Kaidou as a failed Joy Boy who fell into depression (which is more or less what his character is about, but since Oda didn't work it enough many found out of place that Kaidou's fight turned into a "Having fun?" dynamic even though it made total sense); etc.
It's obvious Oda has some main themes more or less thought of; it's no coincidence that "don" (which people like Tom defended) sounds like "dawn" and is the sound drums make (e.g. during the Skypiea party), or how the sun is a symbol used by pretty much every oppresed people in this story, is directly related to freedom (Sun Pirates) and revered by the Shandians and Elbaf giants, or how the yet-to-be-explained quote by this Willie Gallon guy (which Oda put in a chapter with no apparent reason) totally sounds like Vegapunk's explanation on how devil fruit came to exist. Just too many of these themes perfectly fit the figure of Joyboy from real African folklore and it seems obvious Oda made some research on it to build the foundations of his work.
So, to summarize, could Gear Fifth plus Nika have been handled better? I think so. Is it a good idea still? I think so too.
Well said