the point of marxism is to not deal in utopias

Marxism involves an end goal of a moneyless, classless, stateless society. It absolutely has some utopian elements, even if subsequent Marxist revolutionaries were justifiably more practically oriented.

The reason they become liberal bullshit is that they essentially describe these things as ideologies in themselves, that they are the end goals from the start, and that basically paints any socialist that is ok with previous states as a distinctly evil person to the core and someone who wishes harm and torture upon innocent people.

This is liberal bullshit, yes, but I would argue this use of "authoritarianism" is not the only use of the term. In addition to (occasionally) being directed at the U.S. police state, it's also directed at Nazi Germany and the various fascist dictatorships we propped up during the Cold War (e.g., Pinochet). The term has a real, useful meaning outside of its propaganda use.