To defeat this you need intense oversight, but then you yourself become the man with an iron fist.
This is a super common theme whenever you dig into anything socialized. It works great when everyone understands the system and is dedicated to the work, the mission. But as soon as a single atom of "I can get away with not doing my full part" seeps in, it's like a seed crystal that eventually collapses the whole system.
Our desires make us our own worst enemies, and until we acknowledge and openly plan to counter these tendencies, any social structure at some scale is going to fail to them. Unfortunately, the problems we face as a species are increasingly at larger and larger scales.
I'm not sure if we can remain what we would recognize as "human," and solve for this without surrendering some level of executive function to an entity not afflicted by it. Government and regulation are already expressions of this, while retaining our intrinsic nature, but history has demonstrated this is inherently unstable.
In a union context, that could be anything from dues, to volunteering for shitty work, to community service obligations. Unions don't really exercise the power to expel members though, because it reduces their own leverage.
This seems logical. A labor union carries power commensurate with the number of members in it. It is more important for members that they be protected than that they be held to a high standard. If the latter is done, it is in service to the former. That is entirely the purpose of the union after all. No one forms a union so that others can hold them to a high standard of performance.
