Nordic countries don’t have socialism. They have social democracy which is capitalism with a solid social safety net.

Marxism fails from the start because it’s entirely predicated on the state being a monopoly on violence to enforce societal norms. Marx postulated that after a proletarian revolution, the State would be an instrument of the proletariat, used to forcibly take State ownership of all means of production and shift to a socialist mode of operation, after which the role of the State will diminish until it becomes solely a tool of economic coordination and ceases to exist as a State in the traditional sense.

The problem with that is that it still relies on having people running the State, and you end up with the same kind of people that seek power. Only now you have given them absolute power over the entire means of production too.