The USSR was abolished and I can't imagine it simply returning in its previous form as if nothing happened, no matter what else occurs. But I suppose that fact in itself doesn't really answer your question, since you're not just asking about the formal state with its constitution and symbols, but also about its "spiritual" legacy. Obviously this can be potent. I am reminded of an
article by the Communist Party of Greece that was written while Lenin's statues were being torn down in Ukraine.
It is hard to substantiate this memory without, as the Greek article does, point to the concrete achievements of the USSR. The legacy of the USSR is not some pure idea, formed in people's heads. For many people living in its former territories, it is the memory of a period that they witnessed themselves, i.e. it is tied to their actual lived experiences, it is the memory of having lived and worked in a socialist state. But by themselves, these are individual memories that are widely divergent. They will shoot into all kinds of different directions if they are not unified by some coherent political analysis, some kind of collective processing of the past.
Here I would qualify the "fanaticism" about the USSR. I would say, yes, absolutely, we need the kind of passion and righteous fury of the article that I linked to, but this is rooted in a far deeper study of Soviet socialism. The Greek party drew up their
Theses on Socialism, not in order to set a verdict about it in stone, but as a living process, because they know that it is essential to understand the 20th-century construction of socialism, and the eventual counterrevolution, in order to inform their own programme for socialism today. You cannot propose a communist programme today without dealing with this legacy. And steeled with that knowledge, you can fight back against bourgeois ideologues who say things like: "You're talking about socialism, while the Ukrainian people are destroying its symbols."
That should also answer the question about propagating the virtues of the USSR. Obviously that depends on where you are and how you would conduct that sort of propaganda. No doubt communists operating in Russia would engage differently with the USSR than Greek communists do, let alone American ones. It would be pointless to go in the streets in the west today to campaign for the return of the USSR. Even in Russia, it would be pointless if you only proposed to add red flags and other trappings to the presently existing capitalist dictatorship. But the history of the USSR has to be absorbed and assimilated as part of our history, and it should be a part of our arsenal when the need does arise.
Thankfully, communists have stepped up to the plate in this regard. I already linked to the KKE's theses, but they are just one example. I still have to read
Socialism Betrayed by Keeran and Kenny. Back in the 90s we already saw
USSR: the Velvet Counter Revolution and
Another View of Stalin by Ludo Martens,
Blackshirts and Reds by Michael Parenti, etc. And I would bet that there are similar works existing in French, Spanish, Russian, etc.