The galaxy isn’t able to be saved. It is a living breathing entity, constantly changing. The Jedi attempt to “Domesticate” the Force, the Sith like to “let it run free” (when they’re not hiding it, thus why their force powers are so cabin fevery).

Rey is balance. Rey shapes the force to her will only when necessary - there is no need for her to try and control or trap the Force. She has spent years alone, literally watching the world pass her by. Finally, she has reaches out and finds the Force available to grab ahold of. She keeps grabbing on, seeing how much further forward the force will pull her. Eventually she’ll feel safe enough to never let go.

Imagine that the Force is a treadmill. Jedi walk at slow speeds for the longest durations. Sith turn up the speed as high as they can, until they can barely keep up or get thrown off. Rey just uses the last speed it was set at every time, and keeps up with it. Ultimately, it’s about learning to control yourself versus learning to control your surroundings (for good or evil). For Luke to become her true teacher, he had to understand those things first. TLJ is the story of Luke learning that. In that moment of understanding, he grabbed onto the force with the purity and ease that Rey does. His body couldn’t handle that - only hers can.

Or that’s kinda the alignment perception I got from the film.