How would it have been ethical? If their current process was already suspected to be the worse of the two, and their goal was to improve peoples' moods per se,

How would it have been ethical? If their current process was already suspected to be the worse of the two, and their goal was to improve peoples' moods per se, what is the ethical thing to do? Keep people feeling more sad? Or, perhaps, stop being algorithmic in what people see, or else put people in full control of simple sorting (prioritize my "starred" category and sort by date)?