Remember idealist/materialist in a philosophical context is, in its most common use, a metaphysical distinction. Marx’s use of “idealism” is based on this but isn’t the same.

But an important element of Marxism is that it ascribes strategy based on a) class position and b) conflict-aversion. If you are a prole or you just want to play it safe, even as a member of the bourgeoisie, it tells you that socialism is the best way to accomplish that goal, but it’s by the same framework that it can give a capitalist insight on how to practice capitalism with still-more-brutal efficiency if that is what they want.