As with everything else, it's possible to do character development badly, but I don't think it's as bad as you make it sound. Compare Bianca and Cheren with Hugh.I think the "evolution" or development in fiction is done wrong most of the time; someone doesn't change from black to white in the curse of an adventure.
Bianca is going on a Pokemon journey to find her independence as a person. She and Elesa confront her father (who may merely be overprotective or outright emotionally abusive; both interpretations are possible, and you can form your own opinion) but through her interactions with you and Cheren she comes to terms with the fact that the path you seem to be pursuing isn't hers, ending up assisting the professor with research since that's what she finds rewarding.
Cheren's goal is to become the Champion. His use of held items rather than Potions conveys his strategic nature and lends a sense that he has the makings of a strong trainer in him, but when Alder asks what he plans to do after he's on top of the world he has no response. Being the League Champion in Unova isn't like climbing Everest, where "because it's there" is a valid reason to do it; it's a role with a significant amount of influence, and Cheren has no idea what he'd do with that even if he did get it. In the end, N explicitly chooses you as his counterpart over Cheren, who bows out with grace (but still succeeds at fighting his way through the Elite Four, as if just to prove to himself that he was at least in with a shot) and becomes a Gym Leader, using his expertise and wisdom to assist his fellow Trainers.
Hugh is a kid who wants to get his sister's Purrloin back. He shouts a lot at people wearing Team Plasma uniforms, ignoring any nuance in the scenario (like the former Team Plasma members wearing their old uniforms as a symbol of contrition and loyalty to N); he cares about Pokemon, and thinks that things like stealing them and making them sad is bad in the abstract, but he only actually cares about his sister's Purrloin. Eventually he gets back the Purrloin, and he crashes to a halt as a character. The battle in Victory Road is a formality - previous Pokemon games have a rival fight in the run-up to the Pokemon League, so here's Hugh again.