Socialism works just fine in voluntary communities. It’s not the collectivism that is the problem, it’s the force.
Yes, but there are problems with scaling besides the need for compulsion. I’m not sure where the cut-point comes (and with modern computing it might now be larger than it was formerly), but even if everyone is enthusiastic about the project, when a socialist economy is large enough it ceased to function efficiently. It’s all in the Austrian school. I can never remember which critique was which, but vonMises and Hayek took socialism apart on the basis that the information needed to run an effective socialist economy can’t be collected and can’t be efficiently processed by a central authority (one made one point, the other the other).