Accepting that Ingsoc did not evolve from socialism, Oceania's totalitarian regime almost certainly evolved from English democracy with its rigid class structure. Set as it is in London, 1984 likely deals with totalitarian tendencies in the West, and in particular the threat of invasive technologies, secrecy, repression and propaganda (now euphemistically tagged 'spin'). Geographically, Oceania excludes all the historical strongholds of totalitarianism.
Besides, the book is hardly a critique of communism. The heyday of communist sympathies in the West ended with World War II, except for a remnant of party die-hards. The threat of a world dominated by communist ideology was fading fast by the late 1940's, and Stalin was a wretched advertisement for its creed.
Living in the UK, Orwell (like Paul Robeson in the USA) must have been painfully conscious of growing anti-communist hysteria, lies and repression in the West. After the publication of 1984, with anti-communism at fever pitch, he would have been guarded when speaking publicly about politically sensitive themes implicit in the book, such as the invasive, repressive and anti-democratic measures by taken by an Oceania government based in London. With or without Orwell's explicit endorsement, the book speaks for itself: even democracies are corruptible!