As an outsider, I have observed that unions have nearly ruined the SUNY system in New York, where merit pay is a small component of the annual pay increase. It is a classic example of self-selection, where the most productive experienced people leave SUNY for other universities which reward merit, and the most promising newcomers don’t take jobs there in the first place.
Unions sound good to the non-deep thinker ("let's all join together, the man can't screw all of us!") and at one time they were probably needed when industry growth outpaced safety and large firms abused their asymmetrical power. Like 100 years ago or more. Before labor laws.
But given the laws on the books now regarding standard work weeks, worker safety, non-discrimination etc the unions are down to bartering for the right to guaranteed, predictable pay and benefits based solely on seniority. Some rational thought will instantly reveal that unions are set up to protect and, indeed, advance the worst workers while supressing and limiting the best. Mediocrity codified and celebrated.