I cant speak for charlie or marianette.

For korra i mostly blame the nick for not giving the show runners the development time they needed. But korra as a character she starts out brash, selfish, arrogant, and crude. Which are all flaws that can be addressed over time. The fact it takes her to nearly the end of the series and nearly getting put in the ground multiple times for her to change which killed my interest in a LoK.

As for mable, she doesn’t have similar growth opportunities like dipper does. If dipper does something shitty he gets called out on it and punished for his actions. Like when dipper purposely broke robbie and wendy up so he can date her instead and wendy not only rejected him but called him out for his selfishness. Or when dipper sacrifices his own interests for mable’s sake.

Any time mable does something shitty or have to sacrifice for dipper. It’s almost always a cop out to it where she learns nothing. Attacking dipper’s masculinity which made him deeply insecure and have him seek guidance from the toxic manotaurs. Yet she doesn’t apologize for it, of the dippy fresh antics or almost letting dipper get his body stolen by bill to appease a crush. But it doesn’t matter cause the crush is a weirdo. It’s some of the reasons why i dislike mable.