At the end of the day it comes down to these two lines:
After his greatest failure, Luke hangs from the side of cloud city, lacking weapons and a hand. Completely defeated, he calls for help… anyone.
After her greatest “failure” (this is her one moment of weakness so far) Rey escapes from the Supremacy, having failed to bring Ben Solo back. But her first line back is:
Yeah, I like this!
One thing that’s easy to forget apparently is that at the end of Empire, Luke’s back in tip top chipper shape (already has his hand back), confident and with a plan to save Han being his last line in the film. Whereas Rey’s last line in the film is one of fear and doubt.
It’s important to recognize the context of that scene: in Empire, the exchange concerns Han. They’ve spent a couple hours getting to the fleet and creating a plan. Luke is confident in this plan, or at least hopeful, which is why he is chipper. But had someone said “we probably won’t get Han back”, everyone would have had darker thoughts. The final shot is bittersweet; Luke hasn’t even addressed the Vader issue.
Rey’s scene is a bit sad, but is quickly overturned by Leia’s positive comment. Had Leia been a bit more concerned there would have been more drama. Instead, the final shot is the Resistance all smiling ready to fight another day.