So, I finished going over the quoted part, and Marx is talking about specifically the type(s) of idealism that I do not subscribe to. He is addressing specifically the types of idealism that posit that only material stuff and mental stuff exist, and that the latter has some sort of 'primacy' over the former. My view on this sort of idealism is echoed by what you quoted, and I find that type of idealism rather silly.
The quoted part does not address the type of idealism that I subscribe to, one which posits that non-material non-mental stuff, like what mathematicians study, exists as well, and that some of it has no dependency on the other stuff, i.e. it has 'primacy' over, in particular, material stuff in this sense.
So, I finished going over the quoted part, and Marx is talking about specifically the type(s) of idealism that I do not subscribe to. He is addressing specifically the types of idealism that posit that only material stuff and mental stuff exist, and that the latter has some sort of 'primacy' over the former. My view on this sort of idealism is echoed by what you quoted, and I find that type of idealism rather silly.
The quoted part does not address the type of idealism that I subscribe to, one which posits that non-material non-mental stuff, like what mathematicians study, exists as well, and that some of it has no dependency on the other stuff, i.e. it has 'primacy' over, in particular, material stuff in this sense.