In case of Luke it's understandable since it was about the only way to get out of that hellhole and beside he knew shit at the point (you can notice that he took what Obi Wan told him not very seriously and only seeing the corpses of his uncle and aunt he believed the Empire is shit). Also Owen tried to dissuade him all the time, and he couldn't really tell him the reason why so he did opposite by coming out as an old grumpy fart - the fact he really was an old grumpy fart even when he was young didn't helped too.

Leia was an Alderaniaan princes, that means she was raised in the turboliberalism, the fact she was later one of the most sensible people in SW speak volumes how much she did to overcome it.

Han was iirc heir of stupidly big fortune on Corellia which he dumped and never looked back because he wanted adventures. For comparison, that fortune and power he dumped was so huge that by mere virtue of belonging to the clan his stupid cousin Thrackan rose to galactic prominence even despite numerous fuckups, real Louis Bonaparte hours.

Also not everything post Disney is fan fiction, Saw Gerrera was the most canon rebel possible.