I've heard many arguments for the "why didn't they build a planet from the movies? harry potter did that". While I think building a well known planet from the star wars universe would have been more captivating to some, it wouldn't impress the entire audience. The reason Harry Potter did so well is because literally all the movies are based around Hogwarts Castle. Diagon alley was also visited many times by the characters during the movies. However, once a planet is done in a star wars movie, you never really go back to it. With this, everyone has a favorite planet and has a different opinion than other fans. Personally I'd love to have a Coruscant area or a Hoth area, but I know that others wouldn't have that as their first choice.
Now I know that the imaginners were going to do a Tatooine area and got far into development but it got scrapped due to high level exes and Kathleen Kennedy wanting it to tie into the sequel trilogy. However, if Tatooine was built, it wouldn't of satisfied everyones idea of what a story wars story is. It would have put you into the world of star wars yes, but not an ideal version of everyones star wars story. I like the idea of an outside star wars story planet. It brings something new to the universe that is not based in a movie, but based in a fictional but tangible experience.
But yeah, they should've made two different lands. I'd be much more excited and more willing to spend my money if I knew that Florida had a different Galaxy's Edge. But Disney knows that most people will either just go to DL or WDW, not usually both, at least not the GP.