So I spent some time thinking about what to put in response to this, because I find the notion that Pokemon Sun and Moon have good character development as, frankly, laughable. But given the high levels of praise this is getting, as the only dissenter - again - I suppose I need to make some effort to explain precisely why I think the way I do.
See, this is the thing about NPCs - they're NPCs. They cannot properly drive the story forward at the expense of the player's involvement, which is exactly what happened here, what happened in the last two generations, and what will probably happen in the next, because Game Freak have absolutely no idea how to write a different story or how to create a compelling cast. Same old each time might work for gameplay, but it does not work for plot, and characterisation will always be minimal if you are not directly witnessing and/or controlling a character for the vast majority of the game.
Just having a personality change all at once in response to a major event is NOT character development. Part of it, yes, but not all of it. It's something that happens gradually over time, in response to many different factors, and isn't focused solely on pivotal, life changing moments. The simple fact of the matter is that, because these characters were off on their own journeys, we never got to really see them develop properly as characters. We saw one or two defining moments. That is not character development; that's forced change with barely any context.
You also need to have a character initially to be able to develop it, and the NPCs in Sun and Moon were just as thoughtless and uninteresting as those in Black and White, and X and Y. Shove them in my face as much as you like, you can't create something out of nothing.
You cannot develop a character off-screen, and one or two pivotal moments does not define a well thought-out, well-written character. They need backstory, and gradual change to existing personality, and above all, they need to be in the player's story, not just in the player's face. Just bringing them in from time-to-time is not going to cut it; it's piecemeal development without context, and therefore utterly meaningless material. I see a start, and an end. I see hardly anything of the journey in the middle, and THAT is what makes character development.
One needs to see the whole process, not just select bits and pieces of it, and until that happens and these NPCs are made into player characters or proper travelling companions with a story that intertwines with your own that you witness in its entirety, I'm afraid that as far as I'm concerned, character development in Pokemon games will always be second-rate and a point against the games rather than a point in their favour.
So that's a resounding "nay" from me in response to this. Character development was handled no better in this title than it has been in any other. If anything it was handled even more poorly due to the frequency of appearance of some of the characters, which is hugely ironic. When Game Freak take the logical step and have these characters travel with you (and, regarding antagonists, give us proper backstory and infrequent story cutscenes that happen at times other than when you're about to foil their schemes) then they might begin to craft meaningful development and relationships. Until then, though? They're going to keep dishing up the same disappointing, mind-numbingly tedious rubbish each and every time.
