The general style is called "socialist realism" with some variations of brutalist architecture. One of the reasons of the weird structural appearance in many buildings are the various ideological constraints by the ruling elites, that the architects had to abide or (often) bend around, if they wanted to express some bit of unique individual approach. Also, due to the slow adoption of new construction methods and materials, a lot of additional compromises had to be considered on top of the centralized economics of the supply-demand chain. These things are really not cheap to support and renovate, since this part of the plan was more or less an after thought.