The thing many people overlook is that the USSR was less interested in achieving communism than in co-opting any other attempts at achieving communism. This, in part, led to the Sino-Soviet split and the split with Yugoslavia. But even before that the USSR was literally founded on the Bolsheviks eliminating all other communist movements in its sphere of influence: starting with the actual soviets (bottom-up worker councils and worker cooperatives dissolved in favor of the central Bolshevik bureaucracy), the massacre of the anarchist movement in Ukraine under Makhno (which prior to that point had fought alongside the Bolsheviks against the White Army) and of course the betrayal of Spanish anarchists that led to the fascist dictatorship of Franco - the latter being something Orwell experienced himself and forever soured him on the USSR.
The Bolsheviks' (and their ideological offsprings' in China, Yugoslavia and the various countries whose movements they co-opted) idea of establishing communism was to do so with the iron fist of the vanguard party that would do all the work of preparing for communism until the unwashed masses of the entire world are sufficiently educated and enlightened to spontaneously erupt into global communism and the state would just voluntarily wither away after having served its function.
Anarchists argue that the fundamental mistake of this approach was to assume centralizing all the power previously held by a capitalist (or proto-capitalist/monarchist) state in a vanguard party is the antithesis of communism and creates perverse incentives for the party given all that power while also being told their function is to give up all that power eventually.
To paraphrase anarchist thinker Bakunin: if you're beaten with a stick it doesn't change anything if it is called The People's Stick, there needs to be no stick. If power corrupts (and absolute power... you know the drill) then we can't expect to pass the power previously held by those we despire to another group and expect them not to become equally despicable. Instead anarchists believe in building bottom-up power structures and abolishing hierarchical power structures.
> [in China] we see that successful communism requires
To be clear as this is a common misunderstanding: just like the USSR, China has always been careful to identify its politics as ideologically communist but not its system as communism. Communism is a class-less, state-less society so "communist state" in Leninist parlance should always be understood as aspirational rather than descriptive. China hasn't achieved communism, China wants to achieve communism, or so its vanguard party says.
Marx was fairly explicit about what communism is and neither the USSR, nor any of its ideological offspring were that. Arguably prehistoric societies existed in a form of "primitive communism" but except for anarcho-primitivists few people think abandoning all human accomplishments is necessary or helpful in achieving communism.