People pay attention to their material interests. In most cases, you can get through to working class people despite ideology. Can’t win everyone over either and that’s ok too.
Ultimately, results matter. My country started semi feudal and it was under socialism that it industrialised, electrified, developed universal health care, built homes for every working family, etc. Sadly the coup in 89 ended that, but it doesn’t have to have been perfect to have been good.
FWIW I don't even think USSR and its satellite states were socialist in any meaningful sense. Socialism, after all, is the common ownership of the means of production. But most of the populace on all those states were excluded from governance, and thus from any effective ownership. So, in practice, it was collective exploitation of the workers by the elites under threat of direct physical force - strictly worse than wage slavery. Some orthodox opposition Marxists in USSR even claimed that it was the perfect example of what Marx originally called the "Asiatic mode of production".
It is worth pointing out your observation applies to lots of post-colonial societies, too. Socialism took Tanzania's literacy rate from about 10% at independence to 80%+ in a generation, and IIRC it also doubled its agricultural output in that time by organising farming along collective lines. Life expectancy rose substantially too, though I forget by how much.
(So much for empires being about spreading civilization, eh?)