Is there validity to the debate within small pockets of the Jewish world to fold Yom Hashoah into another remembrance day such as Tisha B'Av or the 10th of Tevet?
From a liberal Jewish perspective, the themes of these holidays (remembrance and mourning) fit squarely with each other. As I see it, the issue revolves around the ancient Jewish tradition of merging secular, historical commemorations into spiritual or ancient agricultural festivals. For example, the night of remembering the Pesach offering was merged with the week of celebrating the springtime harvest of barley (Matzot) giving us a week long Passover celebration. It may be that the merger of holidays, to combine themes and to widen the breadth of the meaning of the holidays, is a way of continuing to make relevant holidays whose original focus is no longer held sacred or meaningful by current or future generations.