Most employers will allow changing teams/managers internally. Also, you can discuss it with your employer and if you can convince them that you will be able to be productive and relevant without the need for a manager, some employers will actually entertain this request. Several startups actually have a very flattish structure and very loosely defined hierarchy.
> The employer used its "monopoly" to force management on me. That's cured by my ability to try to get a different job at a different workplace, yet somehow a closed union shop is different. It's a double standard.
It isn't a double standard. A closed union shop is clearly different, because it is not the employer's choice/will, but rather a legal binding. In the absence of such a binding, there wouldn't be any closed union shops. There is no legal binding on employers to assign managers to employees. It is an employer's choice/will/culture.
In a closed union shop, the worker who doesn't want to deal with the union isn't happy, and the employer isn't happy either. Both, the worker and the employer cannot do anything to change that. In your "forced management" example, it is just you who are unhappy, and you can try to make changes in your existing workplace with the possibility of some success, or find a new workplace.