... especially to those engaged in narrowly specialized, monotonous and depersonalized work in industrial plants, when the machine tends to dominate man — was important and eloquent from the point of view of social ethics...
(leaving Soviets' mistakes aside - if we talk about realities and socialism purely)
Hadn't Pope seen any factory then in the non-socialist, christian west, where workers were not different? He should have mentioned workers in the west too. At least, workers in Soviets were trying to speak their voice. Workers in the West had no voice, still not..
From theological point of view, Pope contradicted with St. Paul who had supported worker movements in Phisidian Antiochia where he gave his first speech during the worker revolts there and the result was workers were winner there. But, St Paul was a tent maker, a worker, unlike these religious scholars today, priests, imams, etc etc. who don't understand workers..