DaasYochid said that
“We don’t universally keep a day to commemorate Tach V’tat, and Shabbos is not a commemoration of the Crusades”
Tach V’tat may not be universally commemorated but it is commemorated and considered the norm to do.
And “the Shabbos is not a commemoration for the crusades”. Well we certainly are saying a tefillah about it EVERY shabbos year round, so if those Rishonim that instituted that, then SURELY the Holocaust which was multiple times more horrific should perhaps more certainly have a specific tfilah every shabbos. Just like the crusades.