You're confusing Marxism and communism and socialism - with totalitarianism - which isn't a given. The Paris Commune wasn't totalitarian. Vietnam and Cuba aren't really, either. There's other Communist theorists, like Bakunin and some others - that tend to push more in an Anarchistic direction... So my point is Marxism is actually multiple tendencies, in reality, and mostly a school of dialectical economic analysis - of the inevitable failures of capitalism, as a model.
As for "ANTIFA" - there's a bunch of different tendencies which come together under that banner. Everything from Marxist-Leninists, to Maoists, to Anarchists, to Agorists and Voluntarists...even some obvious Democrats. They're mostly united by what they oppose - racism, jingoistic nationalism and militarism (in theory) - more when a guy like Trump is in office, sadly...than when a Biden or an Obama come to power. With some, their ideological commitments (or lack thereof), contradictions and inconsistencies will then come to the fore... But nothing is really universal, because they organize around (allegedly) shared points of unity, and some ideas - like mutual aid, and sometimes solidarity (with each other, and perhaps people of color, the dispossessed - hell, even the working class in some instances, but obviously not in others). There is NO GRAND LODGE of ANTIFA. There are no Charters, or hard and fast rules - except perhaps within local groups who apply that moniker to themselves.
Which can lead to some problems - including COPS and Feds and Spooks putting on Black clothes and masks (like "Umbrella Guy" in Minneapolis - identified by his ex- as Officer Jacob Pederson of the St. Paul police - who started the rioting over George Floyd, there - at the Auto Zone, before the State moved in to Prosecute Chauvin and his accomplices), or getting "assets" and informants to do the same. The team that ignited a lone aging cop car, left unattended, right in the middle of an intersection on Beverly Blvd, right in front of a BLM march (that was scheduled to be peaceful and nonviolent), would be an example. Those guys look to have been "assets" if not cops and agents - who came prepared with tools and an accelerant, an igniter, spray paint cans, etc.. One act like that at a nonviolent event - can give the cops the excuse they're waiting for, to declare an "Unlawful Assembly" - begin deploying teargas, and assaulting the peaceful protestors...the Agent Provocateurs rarely, if ever, get picked up.