Could just as well be a vision for the "new man/woman" of socialism, which "he'll plow the fields, then write a poem" (e.g. not just be a mere worker cog, but a worker + creative intellectual, a whole personality).

Reminds me of a 1960s movie (can’t remember the title) where Peter Sellers plays an enthusiastic British communist who envisions what life must be like in the Soviet Union: “In the day, working the corn fields. In the evening, ballet!”

It’s a fun idea but no, it’s not about Stalin - Mayakovsky refers to various Bolshevik leaders explicitly and often by name. It’s Mayakovsky, not Mandelstam.