If one wanted to observe Yom HaShoah in a spiritual/ Torah way, like other days of tragedy are observed according to Jewish law and tradition, he would do so by fasting on this day. But in Nissan we are not supposed to be fasting. That already shows you how the invention of Yom HaShaoh is contrary to the spirit of the Torah, as we are unable to observe this day in the way that the Torah tells us to observe days of tragedy (erev Shabbos Chukas, Tisha Bav, etc.)
The original proposal was to have Yom Hashoah on the day of the Warsaw Ghetto Uprising, which was erev Pesach. However, this “uprising” was against the Torah, as explained at length by the Gaon Rav Miller. (Look it up.)