Depending on the execution of Leia dying/Kylo being healed, you could say that Rey is so ashamed of her actions that she decides to go full hermit mode (especially if she blames herself for Leia’s death). As far as plugging plotholes, maybe a little tweak to the end of Kylo’s hangar speech:

“Skywalker & Palpatine, fighting the same old war. Alone, all that waits is the Dark Side or death. But together, through our bond, we have the power to grant the galaxy a fresh start…together."”

Or, if that’s still too soft-hearted of Kylo Ren:

“Skywalker & Palpatine, fighting the same old war. Alone, all that waits is the Dark Side or death. But together, through our bond, we can restart…make things the way we want them to be!"”

The ending bit is more passionate/self-centered on Kylo’s part, and it’s a direct callback to what Anakin told Padme on Mustafar in RotS. Even when Kylo’s trying to do right, he’s doing it wrong.