I think unions historically have sometimes been great, and sometimes horrible. Two examples of unions actually making the world a worse place are the police unions and the teachers' unions in the United States.
If you wonder why we can't fix police corruption, it's because the union protects them - so you can't have both. If you wonder why we can't fix education, it's because the union actively defends teachers that are demonstrably bad for learning (and have visible apathy to the point of sleeping in class while "teaching" students) - so you can't have both.
There's more to the world than worker's rights.