We should ignore the Donald Duck thing, it was a temporary celebration thing that just ended up sticking around for whatever reason.
M&G characters like the Fab 5 act as ambassadors for the resort as a whole, they are not tied to the theme of story of the land and park they are in. Like, when you meet Mickey at DAK, he's not part of the story, he's there, visiting, like you are.
At the end, you are comparing a park with looser, more general theming (MK/DL) with DAK, a park with very specific and overarching theming.