Building off my idea above; if you’re one of those people that doesn’t like the way Luke was portrayed in TLJ, maybe you can cut out everything with him and Rey on the island after we see her holding the saber out to him on the cliff. Then, the next time we see him is when he shows up to join the other rebels on Crait. That way, you can imply that him seeing his old saber again was enough to convince him to come back. This would probably involve having to cut out all Snoke scenes, though, as well as any mention of him, thus making it so that Kylo went to the dark side by his own choice, and he’s been running The First Order/ Imperial Remains since the beginning… Perhaps this is too radical of an idea…

EDIT: Yeah, you know what? Nevermind. Forget what I just said in this post. Given the material we have to work with here, Grumpy Luke needs to stay, whether people like it or not.