It (and Animal Farm) were depictions of Stalinism from the inside - historical fiction rather than science fiction.
He was a democratic socialist, which put him strongly against actually existing capital-C Communism which was totalitarian and Stalinist. The "memory hole" bit is clearly based on how Trotsky was edited out of the official history, for example. This article cites opposition to Lysenkoism as a direct influence, as well: https://lithub.com/orwells-notes-on-1984-mapping-the-inspira...
For the "democratic socialist" part I would point out that Orwell sympathized with Anarchists in the Spanish revolution at minimum.
I don't think that's true in his post-Spain days, depending I guess on how you define "devout communist". I would say he was a devout socialist and an ardent anti-communist after Spain.
I am having no luck finding it, but one quote that has stuck with me is where he talks about how if the anti-Fascist forces in Spain won they would obviously establish a totalitarian state which would only be "good" by comparison with the Fascist alternative and would be terrible in any sort of objective sense.