I wasn't looking at it as a dramatization about the funeral arrangements for Stalin so much as a commentary on the atmosphere of the state he created. That the Terror happened in this year, or that year, doesn't change the fact that it happened. That it was what Stalin created, and what the main characters were fine with, until it was their turns on the spot, and that they were emblematic of what sort of person ends up in charge in such a polity.
I think I was looking at it more of a fantasy expy state that cherry-picks historical parallels to make its points, like in Song of Ice & Fire or the Kushiel or Locke Lamora books or Chris Bunch's Numanti trilogy, than actual Soviet Russia. The rushed kangaroo-court nonsensical trial of Beria or the cleanup of the dacha were clearly not remotely historical, but intended to keep the audience from thinking that Krushchev and company were not the good guys.
But I can see how it would all piss you off, because there are similar buttons for me, that would render a work utterly unwatchable if it pushed them.
As for your casual dismissal of Beria's reforms, don't forget that Deng Xiaoping conducted similar reforms in China and China has become an economic powerhouse and mixed economy while not ceasing to be a heavy-handed authoritarian state (though no longer a totalitarian one).
Beria's reforms could have created a Soviet economic miracle in the 1950s and 1960s without reforming the political system and without unleashing the separatism.
I see nothing better about that scenario. I was not doubting Beria's competence or capacity to succeed, I don't see how the world benefits from another country like China. I also generally tend to find myself supportive of separatism in general.
Your description of Beria & his reforms is not unlike Germanophile Alternate History fantasists who create scenarios where Rommel leads a coup to depose Hitler and utterly defeat the Soviet Union, and maybe even the Brits, too, while, of course, dismantling the concentration camp system, and purging the anti-Semites and racists. I just don't see the appeal of a large, powerful, well-run authoritarian state with nukes and a good-sized chunk of prime geopolitical real estate.
From the point of view of a Soviet head of state, that clearly isn't a smart move, but as I am not that, nor ever likely to be sympathetic to anyone in that position, I don't really see the problem with that in the grand scheme of things.
“Tolerance is the virtue of the man without convictions.” GK Chesteron
Inde muagdhe Aes Sedai misain ye!
Deus Vult!
*MySmiley*