What you’re talking about is the “authoritarian” part of the progressive authoritarian equation.
As the opposite of conservatism, progressivism is about societal advancement, elevating the average well being in the country, which on it’s face Communism is explicitly about. Or are you arguing that Stalinist Communism was conservative, trying to uphold the values of the historical ruling power structures?
Authoritarianism explicitly opposes political action, attempting to eradicate it entirely. Progressivism is rooted in it.
Conservatism is not defined by “upholding the values of the historical ruling power structures”. A dog being wet doesn’t make everything that’s wet a dog.
Stalinism in practice was extremely backwards, ironically anti-communist, and conservative with its strict vertical power structure (traditional for Russian empire) and promotion of Russian nationalism (Stalin explicitly names Russians as “elder brothers of soviet people”). Stalin’s authoritarian approach also agrees with conservatives’ preference for strict social order models. Political activism was persecuted under Stalin in the same manner - and often by the same people - it was persecuted in Russian empire.
The founding myth of the empire - “Kyiv is the mother of Russian cities and Russia is the Rus” was not only preserved, but actively maintained through any means possible. Can’t get more conservative than that.
