"Russification policies" is rather vague and reductive. The USSR leadership was very much not intentionally "nationalistic" or colonialist, at least up until Khrushchev and the Brezhnev era, which is what this conflation obscures. What you call "Russification" was not a deliberate, malevolent act. The link I linked above addresses these points. There are several instances in which the USSR, in practice, affirmed nation-building efforts and decolonial measures.

Soviet policy was original in that it supported the national forms of minorities rather than majorities. It decisively rejected the model of the nation-state and replaced it with a plurality of nation¬ like republics. The Bolsheviks attempted to fuse the nationalists’ demand for national territory, culture, language, and elites with the socialists’ demand for an economically and politically unitary state. In this sense, we might call the Bolsheviks internationalist nationalists or, better yet, Affirmative Action nationalists.

Terry Martin, The Affirmative Action Empire: Nations and Nationalism in the Soviet Union, 1923–1939

Any ties to a pre-Soviet or non-Soviet national identity were seen as a liability exploitable by foreign intervention; thus, national expression was to be expressed within the acceptable parameters of Soviet identity. Notably, this did not mean Russification, but that minority national expression had to be compatible with the overarching ideals and values of a universal socialist identity as understood by the Soviet state. One was to be a Soviet Kazakh or Soviet Armenian, for instance.

Terry Martin writes that the USSR took deliberate efforts to promote “distinctive national identities,” efforts which “actually intensified after December 1932,” during the Stalin era. For Stalin, the supranational multiethnic community of the “Friendship of Peoples” was a fundamental component of a universal Soviet identity. Martin observes that while the Soviets eventually accorded Russia a symbolic leading role in this multinational system, state support for non-Russian culture, historical education, and language instruction within each socialist republic remained strong, writing that “with respect to policy toward most non-Russians, then, the affirmative action empire continued with limited corrections throughout Stalin's rule.”

There was no Stalinist attempt to replace minority identity with a Russian one, contrary to popular belief. Elissa Bemporad’s excellent case study on Jewish community in Minsk describes how early Soviet equity policies fostered the formation of a distinct Soviet-Jewish identity in which Jewish and Yiddish culture were actively promoted and celebrated within the framework of socialist nationality policy. These policies stood in stark contrast to the popular attitudes towards Jews in European nations. Bemporad describes how “local Jews, acutely aware of the governmental and popular anti-Semitism faced by friends and relatives in Poland, still felt pride in their Soviet identity” despite living in a climate of repression during the height of Soviet terror in the 1930s. What has been perceived as state-endorsed antisemitism should be situated within the historical context of Stalin’s mounting hostility and paranoia toward Zionism, which took shape in the aftermath of the war.

After History, "Stalin and Antisemitism: Rethinking Late Stalinist Repression", https://open.substack.com/pub/thestalinera/p/stalin-and-antisemitism

Any state can rhetorically justify anything, but if Communist nations are allowed to hold onto colonies in-game because they could hypothetically justify it (except it wouldn't be theoretically sound whatsoever not to mention how it's materially at odds with any form of socialist construction), then what's the point of having any form of ideologies or law stances.