A writer can allow the reader/viewer to fill in some gaps, yeah. Such as so-and-so background character's profession or personality.

But this? This is a major arc in the trilogy. Luke's training as a Jedi is the most crucial aspect of his character development.

What was Luke even doing between episodes? ROTJ feels like it's taking place a good solid two years after ESB. And Luke and Yoda's last conversation clearly happened when he left for Bespin to save Han and Leia.

Let's really examine Yoda's claims. He said there was nothing more to teach Luke. He said it was unfortunate that Luke left before his training was complete. As though the confrontation with Vader on Bespin was the final test: resisting the dark side, but Yoda wanted to help fortify Luke's mind first.

But he states that one more confrontation with Vader is required. What is the nature and outcome of this final confrontation supposed to be? Converting Vader back to Anakin? Destroying him? Are they one and the same thing? If not, and destruction is meant to be a literal killing as Obi-Wan seems to argue: an apprentice becomes a Jedi through murder. And Luke refused to murder his father. And thus by that logic, never achieved the rank of Jedi.

Did Luke becoming a Jedi depend on Vader making the choice to become Anakin again? That's like if McDonald's would only hire me if my father promised to eat their egg McMuffins every morning.

Surely Jabba's pupils being able to dilate is far more of a concern than these simple story elements. Surely.