The problem is that compensating everyone the same, or even on the same scale, can never be "fair", neither to the company nor to the worker.
Without being too specific, I've seen it all regarding collective bargaining. I have worked non-union in two different locations. Signed union cards and watched the first contract be negotiated in both locations. I was ambivalent about the union the first time.
The second time I watched it transpire because there was a 15 dollar per hour difference between workers doing the exact same job. I was in the middle and I agreed to work for my wage. I can't blame those on the lower side signing wholeheartedly. There was no clear path for advancement. No way to prove your value and see raises commensurate.
One 10 year plus employee was making 10 dollars less than peers and less than a new hire. Yes, a new hire negotiated a private starting wage at the higher limit.
The company then wondered why they got union cards signed in their direction.
As to working conditions, the sorry workers always "roll the bosses for their lunch money". They hired a worthless guy against the quiet suggestions of us workers. This person was a horrible employee in every way. The union finally unofficially dragged the company by the hand through the dismissal process. I do not exaggerate on this. Thievery of company and worker property. This worker was going to disappear if they didn't disappear if you catch my meaning.
No helpful suggestions by the union have been considered. We offered a 2 tiered pay structure to value the higher skilled workers. (It wasn't going to be 15 bucks per hour though.) Nope.
The best worker we had helped negotiate the last contract. The day it was ratified he gave two weeks notice. He took a job making at least 50k more per year and then showed back up on-site working for us as a contractor. We laughed and laughed and weren't quiet describing how stupid the company was operating.
Bottom line, for every union horror story you can tell, I'll tell you a corporate mismanagement horror story to match it...