"And Coruscant was going to be in ROTJ but for some reason they cut it out lol."

In the end it didn't seem necessary to show the home planet of the Empire. It seemed more important that we focus on the major target of what we were going after in the movie. So to show Vader and the Emperor in an area that didn't relate to the story didn't seem necessary. Of course, I had a million different names for the home planet of the Empire, but Coruscant came out of publishing. - Lucas: The Annotated Screenplays