The reason I am telling you that classes are not simply any way we can categorize people but instead have specific relations to ownership of the means of production and distribution is because I am explicitly agreeing with Marx that the history of class society is the history of successive societies of 2 broad classes in conflict, defined by their relationship to ownership of the means of production and distribution.
Plumbers are not a class. Managers are not a class. Both are workers, and share the same relation to ownership of the means of production. Power is not the enemy, the system that divides us based on ownership is.
The rest of your comment is a ridiculous strawman of a party that is unaccountable and that dominates all. Nowhere in socialist history has this happened in practice or in theory. The working class as a whole decides who should be in the party and government. The party is a subset of the working class, with the same social relations to the means of production and distribution. You are arguing against a caricature.
As for revolution, it's the only way to change a state historically.
As for "mixed economies," all economies are "mixed" today. What separates them is their principal aspect, and the class in control of the state.