Nothing says you can't have multiple competing unions.
Given that capital is overwhelmingly concentrated into a few hands, the job "market" is also a monopolization. You can get a different job but the owners are always the same
Why don't unions compete with each other? They should be forcefully broken up by the DOJ if they are not competing with each other, just as Standard Oil and AT&T were.
This is sort of the heart of my complaint, they are allowed to function as monopolies. The AFL-CIO has rules like "no-raiding" for affiliated unions that are anti-competitive in that sense as well.
Given that capital is overwhelmingly concentrated into a few hands, the job "market" is also a monopolization. You can get a different job but the owners are always the same