Okay lets consider Vietnam though, or why does this continue to not work? Why do all attempts at socialist states so far not look like what we want socialism to look like? I mean, I know House of Lightnings answer (because they're top down attempts at reorganization, not spontaneous reorganization by the population) and I know what I think are my answers (material conditions make it tricky and there are vulnerabilities we need to guard against being exploited) but I'm curious what others think
Burocratic stalinism, distance from the workers, lack of direct democracy. Creation of the political/government class above the workers
I would say a mix of both. The revolution was really primarily driven by anti-colonial nationalist sentiments with socialism overlayed on top of it out of necessity to get support, so I don't think the great desire of the masses was to achieve a socialist system. It was primarily a peasant agricultural economy and the party tried to jump over capitalism through central planning in the same way that basically every other 20th century peasant-country-run-by-socalists did, with all the same resulting problems. The farmers hated being collectivized, there was already a black market and secret private enterprise going on with everyone party member or not, etc. Then they looked around, said "Well, gues we'll be like Deng" and began the switchover.
Liquidationism, separation of the movement from the proletariat, the absence of meaningful democracy, but most importantly: the collapse of the world revolution.
I would say that assuming my answer "requires" spontaneity isn't fair. No Revolution simply happens and then ceases. They all boil under the surface before variously boiling over at different times. The outliers like the Eastern European "People's Democracies" were straight up political opportunism and the military campaigns like China or Yugoslavia were "Leftist" military organizations filling a political vacuum.
I also don't particularly have qualms with "top down", inasmuch as there will always be a Party and there will always be a Vanguard that carries the movement forward, authoritarian or no, and forces change. So I don't as much have a problem with "hierarchy".
The Stalinist model never adequately broke from bourgeois political organization. The Liberal Democracy Ritual was placed with the Soviet Democracy Ritual. Party organization still existed with the political "caste", interns, functionaries, flunkies, etc similar to political organization in the West. It was expanded dramatically with people reliant on being a political functionary and thus alienating them from their proletariat roots. Mao's attempt to break from this organizational method coincided with the Great Leap Forward and the Stalinist factions within the Party won out in the resulting power struggle. Vietnam, Cuba, North Korea, Cambodia, etc all replicated the Stalinist organizational method.
So the biggest mistake there ultimately was Stalinism rebranding this political and economic organization as "Socialism" or Socialism in One Country instead of what Lenin correctly called it in his time: State Capitalism.
Material Conditions deteriorate so all of the "Stalinist" Parties ultimately become single party welfarist/Social Democrats. "Social Democracy at the Barrel of a Gun". With the promise that they'll at least keep the worker's gains in tact. Aka Reformists Capitalists aka the exact opposite of Revolutionary Leninism. As we can see with the slow deterioration of working conditions in all of these States, they even failed at that.