Without the codebreaker subplot, not only do you lose several terrific and important thematic moments, but from a pure narrative perspective, they don't bring Benicio Del Toro to Snoke's ship, which means the evacuation pods never get noticed by the First Order, which means none of the finale ever happens. So no, they don't get to be heroic by breaking the code (WHICH I LIKED btw, they try and they fail, shit happens), but their plotline is the impetus for the entire third act of the film.