Socialist Policies vs Socialist States
When you demand examples of successful socialist command economies then you are shifting the goalpost.
People advocating for socialist policies are not necessarily advocating for a full socialist state. Saying I want socialized medicine isn’t the same as saying I want us to be the Soviet Union.
To demonstrate the success of individual socialist policies such as socialized medicine, public education, unemployment benefits etc, one does not need to demonstrate that a socialist command economy works.
Nordic countries are market economies but they have also been shaped a lot by socialist policies over many decades. The successes Nordic countries have enjoyed has been a product of both socialist and capitalist policies.
And even if the goal was full socialism talking about command economies makes no sense. Command economy is orthogonal to socialism. War time USA had a capitalist command economy. Fascism typically operate capitalist command economies. E.g. did you know Hitler engaged in one of the largest privatization of business ever up to that point?
According to Noam Chomsky the main prerequisite for socialism is workers control of the means of production. A typical example of this would a worker cooperative where workers own the company, vote on how it is run and split the profits. Nothing about that requirement stipulates that the economy needs to be a command economy. In fact it can be argued that that is incompatible with socialism.
Workers in the soviet union did not have any say or control over the company they worked for.
In this regard it could be claimed Nordic countries are far more socialist than the Soviet Union was, given that worker representation on company boards is a common thing in Nordic countries.