Wat? Luke brings "balance" by reigning in a Dark Side run amok, dismantling an Empire that got too powerful and literally oppressed the whole galaxy. That's the point of the OT. The "balance" is a galaxy with two Sith and enough Jedi to contain them, nothing more.

The Prequel Trilogy is a ham-handed social critique that tries to show you "how democracy dies" and attacks rigid institutions for being inhumane. Any "imbalance" for the Light Side is not even a topic - after all, the Force is just a bunch of nano-organisms in your blood! The prequels don't bring any meaningful element to philosophical issues surrounding the Force, and they are such terrible movies that they should just be ignored; a lot of people now rightly hope they will be remade by Disney, which would be the right thing to do.