The super-weapon didn't target random planets. The first order wiped out the capitol of the republic, thus declaring war. And the information regarding the star map was on the desert planet of Jakku because it's in the western reaches, far away from the remnants of the empire in the outer rim. And that's also why Rey was on Jakku.

If the catalyst for events seem familiar, that makes sense, since in actual human history, events do indeed repeat themselves. And if the Star Wars films have taught us anything, it's that the force isn't just some mystical energy, it's a conscious, all-knowing element that connects and binds everything in the entire universe, and uses known patterns in attempts to balance itself. A known pattern catalyzed by similar circumstances worked to balance the force previously, so it makes sense that those very catalysts would be repeated. That's just the nature of the force.

You also have to remember that this is part one of a trilogy. People flipped shit after Episode I about stupid crap like Jar Jar Binks being annoying, and forced Lucas' hand in changing certain plot points and characters for Episodes II and III. Ironically, if people stopped complaining and just waited to see the whole story before judging it and jumping to conclusions, the original plot would have been much more fulfilling, and would have served to make Episode I the most interesting Star Wars installment. The original plot indicated that Jar Jar was a sith lord, and not a bumbling idiot, and acted to manipulate events in Episode I favor of Palpatine and the dark side. But nobody got it, because audiences are generally very impatient, as well as horrible at picking up subtle cues, as is the case for Episode VII.