That's completely opposite to my experience in the GDR. Neither my aunt nor my grandparents had to wait "decades" to move into their Plattenbau apartments and I can assure you neither of them had been on the "privileged side", their Stasi files make that pretty clear.
For my grandparents it was a giant step up in terms of living conditions, previously they lived in an old house that didn't even have running water in the toilets.
In contrast to that, the Plattenbau apartments had very modern design and interiors, they are still living there happily to this day.