I agree to an extent. However, on the Star Wars thing, I'm pretty sure we have it on record that Lucas wanted to make a Dune adaptation first, but couldn't get the rights. This led to Star Wars.
It's not an exact copy, but it does share a lot of similarities. It also copies plenty of other sci-fi (and a lot from other storytelling, like it's an almost exact copy of the hero's journey) too though. Lucas was (maybe still is) a great artist, and, as the saying goes, great artists steal from other works.It's obvious to anyone paying attention that there is Dune DNA in Star Wars. It isn't a rip off, but it is taken to be used.