Character Development: What I'm Trying to Learn

It's always been my guilty pleasure of not letting characters improve but I just thought that it's as bad as this...

Spongebob never passing his boating exam.  To be honest, he could snap anytime if he were a real person.

Which I just remembered about this kind of constructive criticism which went, "Please let your characters improve.  Letting them fall all over again just for the sake of laughs is silly and unnecessary."  That is, no matter how funny errors are, but character development is always appreciated.  I mean, for example workers do improve overtime when they are given the same set of tasks, can improve overtime until they grow too old for that job.  Pretty much, people bad with Mathematics if they struggle may not become masters of it, but hey they can still improve!