Execution matters. Just because people wanted dual-wielding doesn't mean they wanted the mechanic placed ahead of the lore. One of the reasons I would have argued for dual-wielding over Keyblade transformations aside from personal preference is that the rules and internal logic behind it is better established. It represents the kind of structure that KH3 lacked, and it suffered as a story for it.
It's like, yes I wanted Kairi to have a stronger showing in the game, but no I'm not going to pretend that ReMind fixes her narrative arc just because it patches in some flashy move sets for her. When the attempt to fix the issues with the approach taken towards his game exacerbate the core issues with the approach taken with this game (as
@Twilight Lumiair has put it, style over substance) it's not a real answer to the criticism surrounding it. It shouldn't be hard to ascertain why people remain unimpressed.
And I'll concede from the outset that this is all speculative for now. As is any positive or optimistic reception. We're all on equal footing in making a determination about how this looks to us given the information we have available.
While I agree with the general perspective here, I think on this specific issue there's a case to be made that Sora
should be able to dual wield because Roxas's heart is with him for the majority of the game, and that it actually causes dissonance within the narrative that he doesn't. There's at least a rationale to Sora displaying that power which, I agree, could and should have been built into a potential arc for Roxas.
Moreover, I think the real issue with Sora's role in the story isn't so much exemplified through these more or less superficial displays of "strength" as it is a matter of his dynamic with respect to other characters and the narrative at large. Sora has always been mechanically superpowered by the end of each KH game, but the story has always gone out of its way to position his strength as thematically relative to his connections and the people who believe in him, and help him to believe in himself. The influence and support of other characters have always been shown to shape Sora's journey in a way that shares the collective narrative space: Sora is the protagonist, but the viewpoints and motivations of other characters are given equal weight to his own. In KH3, the efforts of ensemble hardly even register; if Sora didn't explicitly want to bring back half of the cast, it wouldn't have mattered to the outcome of the narrative. Even the antagonists get short shrift, ultimately losing the fight because, meh, can't beat Sora (or, meh, wasn't really trying to beat Sora, which is generally the level of indifference witnessing this game's climax induces).
It's the inverse of the problem with Kairi, where they try to substitute a real character arc with poorly reconciled superpowers and then expect us to forget or ignore the issue, which is that, unsurprisingly, she isn't functioning as a character.
The difference between these examples is twofold in that:
1) Nomura himself has explicitly tied the internal logic of dual wielding to a set of narrative principles which he can choose to contradict if he wishes, but not without causing narrative dissonance which people are only right to point out and,
2) The lore surrounding the Keyblade, how it works, who can wield it, and under what circumstances is actually essential to understanding the larger story, whereas understanding why and how the Organization Data Battles are possible is not. That's not to say that there are no valid critiques to be issued regarding the Data Battles in this vein, but it doesn't necessarily take precedence whereas understanding the manner in which the Keyblade functions is consequential to making sense of many of the scenarios that form the core of the narrative, beginning with the first game.
In general, I think people who play KH are pretty familiar with the norms of gaming as a mode of storytelling, and are willing to be generous in accommodating gameplay decisions which are then reconciled (or not) with canon. Dual wielding could have been just another ability of the Keyblade which Sora unlocks with the Faeries' help. Nomura chose to complicate the matter. Turning the trust we should be able to have in Nomura's decisions as a writer into another reason to blame the audience (for bothering to care?) only serves to underscore how arbitrary the lines of defense for this game have become.
I don't disagree with this reasoning on principle, but it opens up the series to further scrutiny on the issue. Namely, if the strength of a connection between hearts is enough to enable Sora to dual wield, why isn't the same true for other characters? Are their connections weaker than his, and if so, how is that quantifiable (I don't mean scientifically, but how would we as the audience be enabled to recognize that)? Moreover, how useful is it to the story in general to make this argument for one game mechanic: to retroactively degrade the link between other characters' hearts in order to advance the notion that Sora is just special enough to warrant this additional skill set? That would seem to call back to the concern that
@Sephiroth0812 rose: that Sora has been effectively elevated above the rest of the cast in such a way that his presence increasingly renders their relevance precarious, as well as contradicting Nomura's own stated theory of the character as a normal boy with no special powers.
Again, this answer isn't unbelievable, but it might have sat better before KH3 poisoned the well. Actually, that pretty well sums up my feelings on the DLC in general.