Maybe the scriptwriters had a different creative direction and didn't find a suitable role for Randy.
It could be that Randy's character didn't fit the theme or tone of the new Christmas story. Maybe they wanted to focus on other characters to bring a fresh perspective.
Maybe the scriptwriters decided he didn't fit the new plot or character dynamics.
There could be various reasons. Maybe the story didn't require Randy's presence to progress the narrative, or they wanted to shake up the dynamics and introduce new characters instead. It's all part of the creative process behind the movie.
Maybe the scriptwriters had a different storyline in mind and didn't find a suitable role for Randy this time.
Maybe the story's plot didn't require Randy's presence or there wasn't a suitable role for him.
Maybe the scriptwriters had a specific storyline in mind that didn't include Randy. Could be for plot reasons or to focus on other characters.
Perhaps Melinda Dillon simply chose not to be involved. Maybe she wasn't interested in the project or had other commitments. There could also be creative differences between her and the production team.
It's hard to say for sure. Maybe the producers had a different vision for the cast or she simply wasn't interested in the project.
Maybe she wasn't available or didn't get the offer. Could be scheduling conflicts or other reasons behind the scenes.
Maybe she had scheduling conflicts or wasn't offered the role. Who knows?
Maybe the scriptwriters had a specific story arc in mind that didn't include him.