i absolutely adore CoM and i think it has one of the most compelling stories in KH! the organization XIII storyline is one of my overall favorite aspects of the kh series and i think it's better that they didn't leave us hanging on what happened during the year between kh1 and 2 - in fact, because CoM happened, they ended up elaborating upon this portion of the story even more through days, wherein we actually get to experience what it's like from the organization's side! even if you don't care for these games, it can't be denied that the organization plays a very vital role in the story and i think they deserved to get some time in the spotlight just as much as any of the main charas did - ultimately i think it was a good decision to make the game, because it's thanks to that that we really know as much as we do about the org. at this point
idk, i feel that many people have the mindset that charas outside the main trios aren't as important/are insignificant to the plot, but just because they aren't focused on as much or because you personally don't care about them doesn't mean that they don't have importance to the main story, and that there aren't other people who want them to be explored more!
in terms of gameplay, i honestly like the card system a lot!! kh has been shown to experiment with various different gameplay mechanics throughout the series and i think it puts a lot of people off, but personally doesn't bother me much