I mean, supposedly the time between Episodes IV and V was 3 years!
3 years you've got this teenager named Luke Skywalker from Tatooine working for your squad, and your main enemy is a guy from Tatooine who became famous to the entire galaxy under the name Anakin Skywalker, which is the exact same name as the guy Luke claims to be his father.
And people worked with this Luke dude on a daily basis for 3 years in between episodes. Like, Princess Leia was fully aware of multiple direct personal connections to Anakin Skywalker and had been held prisoner by him the same day she met Luke! And she said literally not one word to him about any of this, not one single "so, uh, did you know your dad, or...?".
I mean, just imagine the conversations when Luke was like, "Yeah, I'm gonna defeat Darth Vader and avenge my father... hang on, I gotta pee" and then the door closes and everybody just sits there staring at each other in silence while Leia silently mouths "I'm GONNA tell him! I swear!".