Don't? But if you must, it's a separate civ from Russia; breaking cultural continuity is central to the Communist ideology, a process visible in both Soviet Russia and the PRC. Honestly, though, I'd consider it a waste of a civ slot. It lasted less than a century, and it was a miserable less than a century for everyone involved.
Let's not forget that neither Marx nor any of the other early Communists ever expected Russia to become a Communist State - they were aimed at Britain or Germany, because they assumed that the progression would be Feudal - Industrial - Communist - Utopia and Russia was about as far from being Industrial as any European nation of the late 19th century.
The fact is that there were strong Communist/Socialist movements and/or Revolutions after WWI in virtually every continental European state, and (briefly) a Bavarian Communist State as a result of revolution right after the war: in many ways, the Russian Soviet state was a fluke, brought on as much by the utter incompetence of the Russian Imperial State and the historical accident of having semi-professional Revolutionaries on hand in 1917 as by any Guaranteed Ideological Progress.
IF we want to bring back Ideologies (which I think are a necessary part of the Late Game, post-Industrial World) then Fascism or Communism are things that should happen to your Civ: IF the game gives the gamer a choice in the matter, it also has to show that there are strong negatives to each choice as well as positives, and there are Alternatives.
Just for instance, extrapolating from the industrial progress made in Imperial Russia between 1905 and 1913, a Non-Communist Russia would have been the same major industrial power in 1941 that the USSR was: Stalin simply got there in spite of the disruption of the Revolution and Civil War (which, among other things, removed a large percentage of the engineers and management personnel from the country) and by slaughtering at least 20,000,000 of his own people in the process. You want to go that route, be my guest, but it's not the only route available.
So, I don't think a specifically Fascist or Communist Civ is a requirement for Civ VII. Aside from the loathsome nature of most of the resulting Leaders, it strait-jackets the depiction of late game Ideologies, which should, IMHO, combine the features of Governments and Religions from the early/mid game: the fact that virtually all the Ideological movements included the same kind of 'spread' of their movement that earlier religious movements displayed is telling, and should be in the game in some way. The big difference (at least from Religion as practiced in Civ VI) is that more than one Civ can adopt the same Ideology - but perhaps with different aspects to their form of the Ideology based on already-adopted Civics or Social Policies . . .