I was also a member of a union (United Food & Commercial Workers) 1978-1994.
I didn't get a choice -- the union shop is legal in Pennsylvania -- but in fairness, I didn't have a problem with it.
It was my experience that the union's primary strategies were (1) to prevent the firing of all but the most incompetent or flagrantly criminal employees, and (2) to address almost all other grievances through calls to political action.
The union took little interest in what were once called "work rules" -- the processes in my shop were largely automated and, so long as basic safety laws were strictly observed, the management was free to run the machinery at whatever speed in excess of capacity they could get away with.
In addition, concerns at individual work stations were seldom addressed. Safety measures such as shielding and "lock-out/tag-out" were rigidly enforced, but if an individual employee were overloaded, things just went their merry way until the situation became unworkable.
Another common practice was to encourage union stewards to seek promotion to front-line supervisors -- this was NOT done to co-opt union authority -- the feeling on both sides was that the employee was usually a moderate who could see both sides of the issue.
In summary, the union recognized it had little real power and spent most of its efforts keeping the membership convinced that despite that, they'd be worse off without it, The management were so cowed by their supervisors that they managed to substantiate the union's case without really trying.
One thing I still remember though -- the name of that union when I first had to join it.
Amalgamated Meat Cutters and Butcher Workmen
"Where does youse want dis side o'beef, lady?" :)