I don't dispute that unions were important and offer some sort of benefit. What I don't like is that most of the big unions in Europe receive a lot of governmental money and become lobbying groups for political parties. I would not consider them independent in any sense of the word.
But that's exactly what a union is: a lobbying group that strives for a better outcome on behalf of its members. "Independence" is not part of their job description. Why wouldn't they talk to politicians, or even publicly support the political parties that are more aligned with their goals? Or do you believe that is a privilege to be reserved only for the rich?
Ah, but that's not your tax money you see; your tax money is being spent on other things you don't like such as teacher salaries. It's other people's tax money that's being used to maintain unions.