> The mayor of NYC is a socialist

> the core tenet of Socialism replacing capitalism

You can say Mamdani is a socialist. You can say the core tenet of socialism is replacing capitalism. But you can't say both. If Mamdani is a socialist, then replacing capitalism is not the core tenet of socialism. If the core tenet of socialism is replacing capitalism, then Mamdani is not a socialist. Those two things do not go together.