I disagree that unions work. It's mainly due to the fact that it treats everyone more or less the same based on some formula. For instance, they make decisions based on an observable set of factors like how long someone has been there and what education and training they have. But anyone that's worked in the workforce knows this is very limited. People aren't the same. Sometimes someone has been in an org forever but is utterly incompetent. Or someone may have all the certifications in the world but be completely useless. So its a dehumanizing sausage factory. Everyone knows two people may have the same title but one is much more productive at their job.

The rigidness also extends to other factors. For instance, working at a bank we were not allowed to move our monitor to another desk. That was a union job. You had to put in a work order have someone show up eventually and move the monitor for you and get paid some fee. It introduces rigidity and inefficiency and there are constant turf wars. Person A can unplug the monitor but person B has to move it, etc. Or they may have to mandate things like "moving is dangerous so you need a supervisor watching as the person move the monitor.

Finally even if they do succeed at paying above market salaries, that introduces a new question: who gets the job? Paying above a market salary will necessarily result in a lot more workers than available positions. So you have gatekeeping. That leads to cronyism as above market jobs are dolled out to friends and family.

A clear example of how destructive unions can be, take a look at police unions that regularly protect bad police. You see that across the board. I've known teachers in the teachers union that obviously phone it in every chance they get (i.e. showing educational videos during class time). This wouldn't fly in a normal work environment, but due to the over-formalization of hiring, you can't just let someone go for being incompetent or just not very good at their job. You have to jump through hoops