My experience has been the same. I was called a management want a be because I did the job I was hired for. I quite and started working for myself at 4 times the pay I received at the union job. I know what you mean. The company then offered very generous education benefits. I took advantage of it and after 5 years of night school (hard work) earned my degree, got out of the union environment and actually went into management... the hardest damn jobs I ever had --- but well worth it.
What these guys were complaining about was the fact that first shift produced 1250 cases of product in ten hours. We came in for second shift and produced the 2000 for our scheduled production and the 750 first shift didn't get and left in nine hours. The next day we left in 8.5 hours after getting the scheduled production plus the 600 that first shift didn't get.
The difference was second shift we all new hires with less than 3 years on the job. First shift all were over 15 years on the job. Time on job was the problem.
The difference was about $120,000 in 2 month's of production.