Kylo Ren not reforging the mask misses the point. In TLJ, when he becomes the Supreme Leader he learns from his failures in order to avoid repeating them; at first he wanted the past to die, but then realizes it’s a terrible idea after Rey rejects his offer. Him reforging the mask further solidifies his growth as a character from TLJ and reinforces the “learning from failure” message.
As far as a fan edit of the film goes, I agree that the mask must stay for obvious reasons. However, I’m interested to see this change because this project is in text form.
I personally feel like Kylo doesn’t learn from his failures in TLJ because he is the antagonist. Luke does, while he doesn’t (and suffers as a result).
In order to explain why Kylo reforges his mask in TROS, you kinda have to embrace the idea that he is still trying to let the past die, at least in my opinion. Vader was a separate person figuratively speaking from Anakin, and he tried and failed to erase all pieces of Anakin’s past. This is what Kylo realizes following his grandfather means in TLJ - eliminating all ties to his previous persona, Ben Solo. It was likely Ben Solo who childishly thought wearing a mask would make him more like his grandfather. So he only reforges it once he feels worthy enough to wear it again, as in he feels he has destroyed enough of his past.
Then why the hell does he stop letting the past die in TLJ? At first he wanted to rule with Rey and create something new, destroying the Jedi, Sith, Rebels, etc., but she rejects him and he just decides to become Supreme Leader of the First Order. Because he’s learned from his failures. He’s learned that letting the past die is a BAD idea.
That’s growth.