Those were not amazing to live in. There were often no shops, no restaurants, no culture, no nothing. And the buildings had extremely thin walls, there was no privacy, you could hear everything the neighbours were doing. It’s possible to reconstruct them to make them quite nice and livable, but they were not designed that way from the beginning. It WAS depressing. The problems were not caused by it being leftist, though. It was the shitty totalitarian regime with central planning and absurdly incompetent leaders.