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The USSR was the opposite of conservative - they were extremely progressive. In the attempt to make a new man, they tried to crush all conservative values such as religion, family (with children encouraged to denuonce their parents) or sexual restraint (free love, contraception and abortion were allowed in USSR decades before the West's sexual revolution).That was also in the revolution's early 1-2 decades.
The USSR turned much more conservative in the 30s and onwards -- including in surprising fields like science. Even arts, which were playing with new forms early one, were afterwards heavily regulated and directed to be towards more classical and petit-bourgeois aesthetic ideals (heroic/lyrical music as opposed to experiments like Stravinsky etc, same for painting etc).
Same for other areas of life -- e.g. homosexuality was soon again an issue, abortion was made illegal again in 1936 (and legal again, but much less touted in the mid-fifties), etc. And of course social norms were encouraged to be conservative and held back, with extra emphasis on hard work, the duty of the citizen, etc. (e.g. Stakhanovites). Most early progressive or anti-family laws were again repealed in the thirties and onwards.
Of course such a regime change also brought some new social conventions and broke some old, like the break with religion.
>As for it being nationalistic - the USSR was itself a conglomerate of 15 nation states, where any nationalistic claims about for example freedom for Ukraine or Georgia were obviously not welcome.
The nationalism was for "mother USSR", which was not much different from the great Russia (before and after). Hence the strained relationships with Ukraine or Georgia (still nationalistic under that context).