It's a great film but it's not about exploring places.
It's about exploring the networked connections of a small group of people.
You're right that the story isn't about exploring. But in the movie, that is exactly what we the viewers are doing. Indeed there are only a few actual storylines that occur over and over in movies, Star Wars included. I disagree with you though, in that I don't think that the SW storyline has anything to do with exploring the networked connections of people, either. The only relationship of consequence in the movie is between Obi-Wan and Vader.
And I also disagree with you in that I think the story is totally Luke-centric. It was the story of "a boy, a girl, and a universe." At the beginning, Mos Eisley was far away to Luke. The galaxy unfolds for him, and he ends up saving it. That was the heart of the story, not some soap opera with sister and dad.
It was ep. V and VI where things started getting all interrelated.
You have a defined group of characters who come from a stable republic who journey from one savage land to another and we learn more about the crew through how these strange new worlds change them.
That's true in that they aren't exploring just to explore. I should have used the word 'adventure'. The main storyline is that there is this huge galactic thing going on, and a farmboy finds himself at the center of it. It leads to a series of dangerous adventures, and his having to learn quickly. A number of good people help him, and he ends up saving the day. It's an uplifting story of how even the smallest of people can do great things.
It's a classic story. But what made it have such an impact, is that this great story is placed in a huge setting of space, planets, stars, battles, and wildly unimaginable things, realized on the big screen in a thrilling way. The soap opera came later, and it's just my opinion, but I think the sequels should go back to the basics of what made the original movie so great.