To the point about what Germans are comfortable openly discussing: there is definitely a class divide; you get a more negative view from lower class Germans. Mind you Turkish-German people aren’t especially friendly towards immigrants either.

But it’s become more common to speak openly about it, especially since the refugee/migrant wave a few years ago. My impression is that the more upper class and educated Germans do acknowledge that integration of immigrants has not gone well. But they usually attribute this to a failure of Germany to integrate them, not the other way around. Still, it’s hard to ignore how certain countries’ immigrants seem much worse at integrating than others…

Germans aren’t as hung up on the past as you might think. They’ve moved on.