The greatest feat of the USSR was showing humanity which way forward is.

It has forever solidified a practical and real point of reference of a socialist experiment not only being some idea in the heads of intellectuals, but a real entity, that did not cave into restoring capitalism.
An entity that every western education system still feels the need to slander and misrepresent as to diminish just it's symbolic effect 30 years after it has illegally been torn apart.

Of course there are countless mistakes – grave ones even – and degenerations to take into account, it was not perfect, but it was closer to giving the average person a dignified life than any bourgeois "democracy" could ever hope to do.