Strongly agree that all socialist movements are flawed. Have you read The Purity Fetish and the Crisis of Western Marxism by Carlos L Garrido? Makes some good points along the lines of the one your comment starts with. [Edit: ebook or paperback and ebook.]

I must challenge your characterisation of China and Russia, though. Heaven forbid we help to end colonialism (USSR), lift hundreds of millions out of poverty (China), or develop from backwards feudalism to advanced society in one generation (both).

And if there's one thing that socialist governments can't be knocked for trying, it's management and planning! The USSR was so proficient, we can thank them for defeating the Nazis, launching satellites, the concept of a welfare state, and a host of other tech. China has gone from having a huge gap between the relations and the forces of production to rivalling the west with the most advanced tech: https://www.aisuperpowers.com.

There's also the attempt by Allende in Chile to introduce Project Cybersyn well before the modern internet took off. The aim was to use technology to improve planning.

I’m unsure what you mean by authoritarianism? Have you read ‘On Authority’ by Engels. One might say that State and Revolution is an extension of Engels’ argument. Part of Lenin’s view on the dictatorship of the proletariat is summarised here: https://www.versobooks.com/en-gb/blogs/news/3228-lenin-s-three-theoretical-arguments-about-the-dictatorship-of-the-proletariat.