There is no example of marxism being seriously implemented, it’s always been used as aesthetics and excuses for authortarian government who want total economical control.

Those governments never implement true workplace democracy or worker control over the means of production.

That doesn’t mean marxism can’t work, just no one’s seriously tried. At a small scale it definitely can work, anarchist communes are often successful, despite the best efforts of governments to sabotage them however they can.