Jotaro is a pretty static character, he sticks to who he is through the whole story never wavering or becoming something else. He is determined, fearless, smart and reliable despite his attitude problems. Really the whole SC cast is pretty static with the exception of Polnareff and Iggy who do sort of grow as time goes on. Jotaro is a bit humorless, but I find how overly competent he is sort of hilarious. I don't understand some of the hate for Jotaro.
Jotaro's personality is a trope that's not really as prominent now as it was when the Stardust Crusaders manga was originally released.