Everyone (except Bingowings) seem to forget that the Death Star was about to blow up.
The entire trilogy is Luke’s “spiritual” journey, and growth as a character. He had to throw his lightsaber away, or else, as many have already pointed out, he would have eventually have been defeated like Anain did year before and turn to the dark side. Being a Jedi isn’t just about killing the bad guys, it’s about a personal spiritual journey, and Luke fulfills that and becomes a Jedi when he “morally” defeats the Emperor. As for the actual literal defeating of the Emperor, well, again the Death Star is literally minutes from blowing up.
(So both goals are being accomplished here.)
Of course Vader eventually does kill Palpatine, but that was to save Luke in the literal sense and himself in the more abstract sense. It makes sense in Vader story arc, and it makes for a more satisfying end than all three of them just blowing up with the Death Star.

All of this is slightly weird if you think about it too hard, but that’s to be expected with a franchise as popular as Star Wars 30 years after it’s release. We must keep in mind that it is after all a film, and a film needs an interesting set of character developments and twists. As long as this doesn’t directly contradict the lore and common sense, but exaggerates it slightly for narrative purposes, then I’d say it’s done a good job at being a good film.