Have you heard about Roma? The communist states tried to help them but in a hamfisted ways like separating kids from parents. They did nothing to actually resolve racism. Many Roma ended up in squalor in segregated settlements. That goes on to this day and improves very slowly. It definitely was not "its moment".
So nice of you to teach me about the roma. I was sure to have never heard about them. /s
The history of gypsies and their segregation is much older though and the regimes inherited much of their attitude based on prior prejudices. The treatment differed in different times and locations. I've heard accounts of casual police brutality and of good integration in the local community and of a "leave everything as it is without engaging with hard problems". None of those was sanctioned on the bases of race theory and in fact the official stance was for equality. Compare it to the US where it was part of local and state legislation. On the other hand, the higher ups in the regimes were often repainted nationalists and common criminals of old so adherence to the ideals was often perfunctory and positive actions and outcomes were falling short of what was possible.
If it's part of legislation, you can fight it. If the official ideology is equality and racial prejudices "don't exist", then any problems are suppressed and you can't do anything.
Soviet union was defacto an apartheid when you consider how non-white ethnics were treated in practice. They just were so good at suppressing everything that it was never "an issue".
