In technical econ terms, the marginal profit of new employees is typically below the average profit of existing employees. A profit-maximizing business only cares that the marginal profit is positive, and will hire until there is no additional profit to be made. A co-op is incentivized to keep average profit per employee high, which can mean reducing headcount in order to keep the average strong. So that's why co-ops can have a sort of exclusive club feel to them.

SV is actually an interesting example which proves how employee ownership can drive prosperity, but the typical co-op crowd doesn't want to talk about it because it's too capitalist-coded. In a way, SV companies show that employee ownership is not some sort of instant cure for everything which ails capitalism.