Do you actually know what Vienna did? Because the overwhelming number of people who reference the city basically just repeat a few dubious talking point about restricting rent.
But you are right, that surplus housing is no longer a thing in Berlin.
I didn't stay in social housing while I living there but I never once heard people complain about it. They basically just didn't think much about it at all and felt it was a good system and then would ask me why the US only makes it for poor people.