although by that point luke was well aware that the force could be used as a weapon by itself (throwing objects at a minimum and he may have known about choking, no idea if he knew about lightning) so he would know the emperor was not truly defenseless.
plus, he tried to shoot an unarmed jabba but fell before he could pull the trigger

don't look for anything in ROTJ to embody deep meaning or sense.

the original intention of the third film was to have been much different.
Lucas was tired of the films and that original (temp) conclusion was scuttled and replaced with a perfunctory wrap-up that provided a revisionist history for a good part of the first two films.
it was a movie that was 'tossed off' by its creator.

on the question of "what would Luke have done"
- well for one thing, he would have been a little more introspective in the first act of the film.
prior to this films events, he had just failed miserably in trying to save his friend, after going against the wishes of his tutor & mentor, he had been left with devastating information that he has to come to grips with ("i'm the inheritor to a bloodline that is capable of incalcuable evil", "Ben, the paragon that i had known had lied to me") , and he had been left with a serious injury.

ROTJ doesn't suck because of the Ewoks, it sucks because it never addresses these fundemental concerns for the character.
instead we have a self-appelated Jedi who goes thru the first act threatenting and then slaughtering anyone who doesn't capitulate to his demands "You should have bargined Jabba, it'll be the last mistake you'll ever make!" and his net goal is achieved by this.
there are no consequences for acting in a 'vengful, retributional way'.
it doesn't matter, because the creator of the film could care less.


a lousy, cheap(in a dramatic sense)) film

I don't think Luke was acting in a vengeful, retributional way towards Jabba. He knew he was outnumbered, it was all bluster. And he did give them a chance to turn over Solo peacefully.

And if by "self-appelated Jedi" the fact that Luke calls himself a Jedi Knight, I always believed that the duel on Bespin was his "trial". When he rejected the power that his father was seduced by, and chose certain death by falling, The Force recognized this and guided him to the vents instead of splatting on the bottom of the shaft. That decision point is when he became a Jedi. That's why the 1997 scream dubbed in rubbed me so raw. To me, that is a pivotal scene in Luke's growth, and the scream was quite frankly worse than the Greedo shooting first bit (which is bad btw).

And Luke does seem to go thru quite a bit of anguish during the throne room battle, so it's not all "Luke and the Carebears picnic."

I do agree that the film is rushed. I would have given anything to see a sequel trilogy. I never really wanted prequels to tell the truth, when the new movies were announced as prequels, I was actually disappointed for a bit. Here's hoping that with the success of the Clone Wars animated series, there's a possibility for animated films post ROTJ.

It's too bad Obi-Wan or Yoda didn't tell Luke that he could block the force lightning with his lightsaber...that little bit of information would've been helpful in his fight on the Death Star II.