Highly recommend reading Domenico Losurdo - Class struggle for more on this.

It gets into how there's not just a single class struggle, i.e. working class versus bourgeoisie, but many different and related class struggles. Both Marx and Engels held this multivariate view of class struggle too, and it was only later that chauvinists, anti-feminists, and imperialists restricted its meaning to the workplace only.

That is a vulgar materialist conception, from those who do not grasp dialectical materialism, as well as those who reject it deliberately. Class reductionism doesn't recognize secondary contradictions that rest upon the base of primary contradictions, seeing each as separate and butchering how contradiction actually works as an engine of change in dialectics.