I do have to admit when I first saw this film, I was a teenager at the time and I didn't even like him. To me he was whiny and lazy. I don't disagree with your assessment of his character either. His primary motivation is saving his friends, and later, that's replaced with saving Vader, and these motivations pull him into deeper troubles, until the end of the trilogy, when he almost gets caught by the Emperor. At no point does he really talk about saving the galaxy or destroying the Empire.

By the third film he is looking more mature but throughout the first two films he is noncommittal, impatient, still whining. In the last film, he is quieter, more steady. He appears to have changed or at least transformed into someone closer to adulthood.