They don't ignore it, even though they might try.
To analyze "pure" capitalism, one has to ignore the state's influence.
The problem is that what one winds up analyzing, by ignoring the state, is an independently oppressive, albeit incomplete picture of what capitalism is.
There you have it. That may be the essence of your disagreement with them.
Your claim is that capitalism is basket of things that includes states.
Their claim, (which is inherent in their very name), is that capitalism can exist without a state, and that this would solve the problems that you have in the capitalism basket.