A New Hope steals heavily from The Hidden Fortress. (So did The Phantom Menace, but you don't mention the prequels if you want to build a case for the defence for George Lucas.) It steals elements of plot, character, and theme. But it also steals the setting, in a sense. The most important lesson George Lucas learned from The Hidden Fortress is: any story set in an "alien" or unknown setting is better without infodump. The Hidden Fortress was made for a Japanese audience and it doesn't bother to explain anything to do with Japanese history or culture as a result - it assumes the audience would know it already. Western audiences don't understand everything, but that doesn't matter - they just get caught up in the story.
Star Wars doesn't indulge in infodump, unless you count the sketch provided in the opening credits. It doesn't waste time explaining who the Jedi are, what the Clone Wars were, what the Empire is, and so on. It just tells its story and the audience follow along, either filling in the details themselves or merrily ignoring whatever background fluff is alluded to. There's no slack in it as a consequence - it is pure narrative verve.
This seems like a simple thing, when you realise that George Lucas is one of the few people to have ever learned it, and even he forgot it when he came to make the prequels. I just spent a few hours in my local city centre bookshop looking through the SF/Fantasy section and trying desperately to see if anything might grab me. None of it does, because almost every book repeats the same mistake. You flick to the first page of the book proper (all such books have an annoying "Prologue" or "Prelude" nowadays - authors don't have the confidence to just begin at the beginning), and what do you get? 99 times out of 100, it's an opening sequence in which the viewpoint characters indulge in strange interior monologues setting the scene for the reader. You don't get pure narrative. You get a narrative in which the characters are constantly making unnatural asides to a reader who they aren't supposed to know is there.
Here's an example of what I mean, taken from the very first page of the Andy Hoare's Rogue Trader Trilogy (available here), Rogue Star. It is not the most egregious example one could think of - just a common-or-garden example of what I am from now on going to call "Bludgeoning Down the Fourth Wall":
‘Helm, seven degrees pitch to starboard! Number three’s misbehaving again. Deal with it.’
Lucian Gerrit, rogue trader, turned his back on Raldi, his helmsman and resumed his vigil at the bridge viewing port. His vessel, the heavy cruiser Oceanid, felt cold to him. The after-effect, he knew, of so long a voyage through the empyrean to reach this far-flung system at the very border of the Emperor’s domains.
A jarring shudder ran through the deck plate, felt in the bones more than heard.
‘If you can’t compensate for a grizzling plasma drive, Mister Raldi, I can always disconnect one of the waste ingestion servitors and see if it’s capable of making a better show of it than you appear to be. Do I make myself clear?’
If the helmsman answered, Lucian wasn’t in the mood to hear. Though a ship to be proud of, the Oceanid was long past her prime. Even in a space-faring culture in which vessels remained in service for centuries, even millennia, she was old. Her homeport, Ariadne Halo, had fallen to alien attack in Lucian’s great, great grandfather’s time. All her sister ships were distant memories. She was the last of a long line. Much like Lucian himself, in fact.
Where once a deck crew of dozens had attended to their stations in the crew pit, now half of Lucian’s crew were hard-wired servitors, each mumbling an impenetrable catechism of the Machine-God. Vacant-eyed and drooling, each monitored a single aspect of the vessel’s running. Vessels such as the Oceanid relied on their like, for many tasks were beyond the abilities of a man to perform. Yet, over the years, the availability and quality of competent crewmen had diminished to such an extent that Lucian was forced to rely on servitors. Though essential in many roles, the hideous machine-corpse custodians were no substitute for a man when it came to obeying orders in a crisis. Each knew only its allotted purpose, and would remain tethered uncaring to its station even were it to burst into flames.Raldi, one of the men of flesh and blood, rather than carrion and oil, onboard the Oceanid, called out. ‘Sir, we’re beginning our run on the rendezvous point. Provided we don’t pick up any ionisation we should be within hailing range.’
Why is it bludgeoning down the fourth wall? Because it constantly reminds the reader that they are reading a book, rather than immersing them in the story. It is an endlessly-repetitive Brechtian distancing effect which reminds the reader at every turn that they are not part of the world which the characters inhabit. By explaining everything, the author sets the reader outside of the narrative and prevents them losing themselves in it.
For counter-points which do not bludgeon down the fourth wall, I direct you to The Book of the New Sun, Kim Stanley Robinson's Mars trilogy, A Clockwork Orange, and the Helliconia books. (And, it is worth adding, that there are elegant examples of infodump in the hands of skillful authors when the book self-consciously presents itself as a story told to the reader by the author: The Hobbit, The Face in the Frost, and The Chronicles of Amber.)