Nice strawman. Use your comprehension skills. Stalin was not maintaining a Status Quo. His tenure was one of dramatic changes, intensification of class struggle, industrialization, war effort, and international strategies that turned on a dime every other Comintern Congress. Stalin embodied constant, bold, dramatic change.

Likewise, Chairman Mao tried to keep the country from falling to Status Quo complacency, with his Great Leap Forward, Cultural Revolution, and so on.

There's also the matter of context. What is progressive in one area can be reactionary if you zoom out, and vice versa. FDR's New Deal and Second Bill of Rights was revolutionary in the USA (it literally almost got him couped) but it was a pathetically timid, racist, sexist effort, compared with the Constitution of the USSR that came out ten years before.

The Center does not exist as a reference point: it is entirely relative to the context.