Yeah part of me wonders why they couldn’t have left the “other” sister as a hanging thread even if ROTJ was supposed to wrap things up. Much like the “pass on what you have learned” line, it’s setting up Luke’s future adventures without necessarily requiring those adventures to be on screen.

I will say Luke getting angry about the sister certainly holds more weight when it’s someone he’s close with. As cheap and silly as making Leia Luke’s sister was, ultimately I don’t think it was a decision that lacked potential for compelling drama. It’s only a shame that that potential was mostly unfulfilled in ROTJ itself.