Capitalism is a mode of production, so is socialism and communism. These are real, material things, and form the base structure of society. Ideology is how we interpret these things, we don’t decide them based on ideology. Ideology is a reinforcing aspect of the superstructure that justifies the mode of production, but it arises from material conditions.

In other words, the way we interact with production shapes our experiences, and thus the way we think and act, not the other way around.

As for class, you’re extending its meaning beyond its intent. It refers to relations to production and distribution, communism fully acknowledges the differences in people’s abilities, wants, and needs. A classless society is one in which all production has been sublimated into collectivized and planned production with equal ownership, ie one economy collectively run and planned.