In watching through the first few scenes of the movie, skipping around to imitate our ideas, I think the opening feels very rushed removing Mustafar and the chess scene.

You can try it: skip to Kylo approaching Exogol, then skip the chess scene. Feels pretty breakneck. The Mustafar and travel scenes let us get into the movie for a minute before dumping Palpatine on us.

I really don’t mind Mustafar as is, so this isn’t an obvious answer. It might be best as it is, even without the meat of the scene, with or without a couple establishing shots. (Just leave it at the theatrical version so no one’s happy!) Leaving this alone could help losing the chess scene in the opening a bit more forgivable.

This finished movie just doesn’t give us much wiggle room.