“So, for that we thank Him every day”
Of course we thank Him every day.
but choosing one day to jighlight said event is appropriate.
Asking Hashem for MEchila on Y”K doesnt mean we dont do it everyday
Remebering Yetzios Mitzrayim on PEsach doesnt mean we dont do it everyday
Thanking Hashem for the Torah on shavuos Doesnt mean we dont do it everyday
Celebrating Nes chanukha, Purim on the days they occured doesnt mean we dont thank Hashem every day
When Satmar commemorates 21 Kislev or Lubavitch on 19 Kislev doesnt mean they dont thank Hashem everyday.
you wrote that it was ” a demonstration and expression of HaShem’s great love of His children, IN SPITE of their connection (or lack thereof) to Him.”
and What a huge demonstartion it was! by celbratign it one day in no way dminishes the thanks w have every day .