My father was a sheet metal worker for many years. He always described the union meetings as a bunch of drunk* old men voting down any spending on training, something that would generally benefit younger men. Even while the pension fund is underfunded and highly dependent on younger men to pay into it.

My only direct experience with a union was when I was working for a federal govt agency. This org was steadily shrinking over the years as automated systems replaced what was once a highly labor intensive process. The leaders of the org worked hard to find a place for the techs who were slowly being displaced, literally offering them paid schooling and training programs. Those who didn't pursue these offers began to feel threatened and voted to join a union of federal employees.

My wife is a teacher. The teachers union exists solely to protect teachers. She has colleagues who are terrible at their job, doing things like failing to teach math for six months. The principals of the school look into firing them and are told by HR it takes seven years to fire anyone. This is in an environment where education colleges are pumping out tons of enthusiastic fresh meat every year. Teachers unions protect the negligent and harm the young.

Does this help you to understand why I am skeptical of unions?

* Literally drunk. The meetings were in the evenings so working people could attend them. Men would get off work, start drinking and go to the meetings three hours later.