As I said in another article, superhero media tends to attract a rather immature readership in the sense that they overreact to things most people don’t care about and outgrow anytime. The characters that they find relatable aren’t exactly the most mature or independent-minded.
They’re like Mary Sues, fulfilling the reader’s desires to be with the other character whilst not being his/her own person. That audience insert is not a true everyman but a child in an adult’s body with little to no real desires, priorities and responsibilities of his/her own.
Sometimes their immaturity is just acting really childish. Take Felicity for example. Her shtick is to say weird things, throw tantrums and start rambling in a bad mood. She’s like a child who doesn’t learn how to calm down, much less on her own.
Superhero stories also have a lot of immature heroes and villains. Their immaturity lies not only in being constantly overshadowed by a more prominent, if not likable, character but also regressing and acting dubiously. They’re not smart, mature people but perpetual kids with no real conscience.
There’s also little to no real character development. Barry Allen could’ve quit his job as a forensic scientist, finding it tedious and unexciting when compared to solving criminal cases in person. Not all scientists spend their time in the lab but forensic scientists probably do and Barry being one, he’s hardly seen in the lab.
When a character does mature, it tends to get interrupted by many things like not developing his/her own persona, getting overshadowed by another character, getting replaced by another iteration and stuff.
But the problems lies not so much in constant changes but a matter of the writers (not) knowing what to really do with them. What the writers going to do with Kitty Pryde if she doesn’t have a distinctive voice to call her own. Outside of comics, she’s a blank slate but even inside comics writers can’t make up their minds on her voice.
Similarly nobody really knows what to do with Superboy, Tim Drake, Dick Grayson, Bart Allen and the like. Whatever character development they have had gets interrupted by a replacement of another permutation and being constantly overshadowed by a more prominent, likable character.
In a sense that their voices never developed because they themselves never really grew up.