Well, the worst tragedy in recorded history was the Mongol Invasions. But, I digress.
Yes, it's important to learn from history's evils. Note - the current generation of Germans have absolutely nothing to do with the crimes of the Nazi regime, so it's not about "admitting a mistake" they simply did not make. But yes, it's about knowing never to let it happen again.
Indeed, this generation is far removed. And there are tons of memorials and monuments across Berlin that stand as grim remainder of the past. It actually kinda feels sad that they have to walk around in Berlin constantly reminded of their past.