Earlier quoted context omitted.
One of my pet theories is that economic growth is surprisingly poorly correlated to economic or social systems except for one thing: Stability. Bring stability, and people learn the mechanisms that works for their society, and overcome surprisingly large differences in type of obstacles. Be it dealing with the vagaries of the free market, or how to maneuver a Soviet-style bureaucracy. It's in fact almost depressing h…
The 70s and early 80s is the USSR were universally regarded as the period of stability. So much stability that the official name of the period is "stagnation": https://en.wikipedia.org/wiki/Era_of_Stagnation This era ended by the USSR assuming the most stable position possible, i.e. dead. So I wouldn't over-promote the value of "stability" as such. Being stable is good if you're in a good place, otherwise it's deadly…
The 70s and 80s provided slower growth, sure, but still growth. As far as I can tell there was no drastic decline in GDP per capita growth for the Soviet Union until towards the very end of that period, when the rapid changes from Brezhnev to Andropov, to Chernenko, to Gorbachev disrupted the already weak growth.
It's not that I'm suggesting everything will grow the same irrespective of regime or system, but that the correlations are much weaker than most people will assume.