What does it mean for workers to collectively own means of production? Am I supposed to own only the laboratory I work at or everything everywhere? What if I decide to change a place of employment? Why doesn't owning it though the intermediary of the state and your representative in the communist party qualify?
It does. This is because the problem is one of 'political economy', a subject that only Marxists and their ideological descendents (namely modern day academic sociologists and anthropologists who nobody reads) talk about. Political and economic structures intertwine and influence each other to such a degree that separating them into distinct categories is rationalizing at best, obfuscating at worst.
The point is ultimately to organize the international proletariat to such a degree that it becomes possible to destroy the value-form (i.e. money), a.k.a the very fetishization of commodity. One of the reasons you do this is because money, though useful in low information systems for liquid exchange, actually acts as a labor-value obfuscation system in high information systems. A very easy modern day example is how the stock market increases in 'value' despite having no relationship to actual product increases (labor-value). This obfuscation creates inherent inefficiency, and creates perverse incentives for economic and political behavior ( hence the many jokes on here about 'line go up'). Transitioning to co-ops doesn't inherently affect the value form, hence it cannot be the end goal of socialism/communism. It is still too alienated. Ironically, Walmart is closer to abolishing value-form than a series of small trading co-ops, it's just that it's interactions with larger society are more largely parasitic and capitalistic in nature than a series of co-ops.
This is part of the reason communism, imo, is so difficult for people in the West to understand, because what we understand to be more 'human' and 'societal' are organizations that harken backwards towards settler-colonial business ventures, rather than taking over and humanizing developments of capitalist industry towards societal goals. You know, 'seizing the means of production'.