I always got the impression that Luke had returned to Dagobah in between films and completed his training. As said, there is a feeling of a decent amount of timing having passed (on the order of at least months to half a year or more) and a distinct shift in Luke’s manner, maturity and mastery on some level of the force. It would be cool to see a few scenes like Luke constructing his Lightsabre but in my mind theyre completely unnecessary and I don’t know how you’d integrate them into the movie anyway without completely changing the tone of the movie, especially at the start with the rescue mission at Jabba’s palace.
Yeah, many others feel the same way you do, which is why the “crawl edit”, which simply edits the opening crawl of Jedi so that it explains that Luke did go to Dagobah for training, has some people excited.