For the people who these houses were built for, absolute poverty, devastation, and squalor preceded mass-produced housing. World War II was incredibly devastating in Europe, leaving millions without a home at all. The communists took on the enormous task of meeting this monumental need, and did so enormously well.
For the unhoused, a solid apartment with basic necessities and the ability to keep out the rain and cold is often the difference between life and death. Communists saved millions of lives.