Hollywood does not make films that are completely accurate... ever. They always change the details for various reasons. The same can be said of most the history books being taught in public schools. But this film does a better job of capturing the spirit of the situation than most Hollywood creations.
I think The Death of Stalin was accurate in the sense that despite the image we in the West had of the Soviet Leadership as this dour, ruthlessly efficient, focused methodical group of supermen, scratch the surface and it was a rollicking fustercluck.
The film captured that nicely I think.