I won't reply to all that because you've either moved the goalposts or misunderstood my original point.
How can you say that without responding? It seems like you ignored what I wrote, with careful, direct references to Marx and Engels. If I am going to put in the effort of taking everything you said into consideration and responding to the best of my abilities, the least you can do is acknowledge it honestly, not dissavow my efforts entirely. I haven't undermined your ability to understand what I am talking about, nor accused you of moving the goal posts, so I'd like respect in kind.
Tankies are quintessentially authoritarian. That's what I've been saying since the beginning. I agree that Marx doesn't advocate for it, which is why I suggested he'd be repelled by tankies.
You've been saying this without qualifiers. Advocating for "authoritarianism" isn't a thing, hence Engels writing On Authority to debunk the very subject entirely. You have yet to meaningfully prove that Communists advocate for a different system and a different process than what Marx and Engels did. Saying that Communists advocate for "authoritarianism" doesn't mean anything, what structures do Communists advocate for that go against Marx?
I'm arguing for academic analysis of self-proclaimed Marxists.
China is Socialist. It practices Socialism with Chinese Characteristics, maintaining a Dictatorship of the Proletariat over a Market Economy. The CPC is Communist by ideology, but of course they haven't achieved Communism yet, nor do they claim to. They tried to directly implement Communism under Mao and later under the Gang of Four, which ended up being a critical error in judgement as the Means of Production were not at all developed enough for it, hence the Gang of Four claiming it was "better for the Proletariat to be poor under Socialism than rich under Capitalism."
The USSR was Socialist. They never achieved Communism, largely due to refusing to interlock with the rest of the world economy. While they managed to provide many critical necessities like healthcare, education, and so forth for free, shutting out the global market led to consumer jealousy over consumer commodities from the west, which led to democratically instating liberal market reforms, which worked against the centralized nature of the economy, leading to its dissolution.