Which has a fantastic pay off at the end of Empire, and in my mind is rounded out partially in Luke and Leia rescuing him in ROTJ but is never fully resolved, disappointingly because he has so little to do in the ROTJ screenplay as it stands, when all is said and done.
You haven’t actually answered my main question. Why didn’t ESB already explore Han’s decision to join the rebellion at the end of ANH? Even if he still had any doubts at the time of ESB (which you seem to be the only person to see them), why didn’t ESB directly explore them? ESB was the proper occasion to do either of those things.
I guess passing the blame to ROTJ is more convenient? You were picking on ROTJ for not exploring something as trivial and technical as getting some rank, while forgiving ESB for not exploring something as major and character-changing as his decision to join the rebels at the end of ANH.