Divorced from that fact, perhaps so - but I see no grounds for divorce. Those characters are there, part of the text, and their being there has an effect. They too are part of the play's setting, if you like - rather than the setting being a set in the Hollywood sense, that anyone from film-stars to tourists can wander through.
Picking up from your comment below, I've not heard the term "real decade", nor have I read much SF, but I'm dubious of it, precisely because it appears to imply this kind of easy separability of different elements of the text. I suppose the "real decade" of Nineteen Eighty-Four must be the 1940s, by Clute's definition - reportedly Orwell even considered calling it 1948 - but I think that would have made it a very different book, even if every other word had remained unchanged.
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Picking up from your comment below, I've not heard the term "real decade", nor have I read much SF, but I'm dubious of it, precisely because it appears to imply this kind of easy separability of different elements of the text. I suppose the "real decade" of Nineteen Eighty-Four must be the 1940s, by Clute's definition - reportedly Orwell even considered calling it 1948 - but I think that would have made it a very different book, even if every other word had remained unchanged.