Any system that aggregates power can be used towards detrimental efforts. Unions aggregate power and as such are heavily dependent on their leadership.
When there was no employment law in the US and you had children working, obviously change was necessary and so unions were able to provide worker protections that an individual couldn't establish for themselves since they had no power against the corporation.
If you look at police unions in the US you can see how detrimental unions can be as well. They are focused on protecting their workers even when those same workers are the issue which leads to a very challenging environment around firing "poor" performers.
Often times what is better is intelligent government regulation. Though that in and of itself is an oxymoron.
Things like mandated health insurance, overtime pay, work hours, minimum wage, these are all protections that we need encoded in law, less so in unions.
The other challenge with unions, is that while one can succeed it leaves everyone else that is outside of the union at other companies completely unprotected.
At the same time, if you think of the largest union, it is all of the workers of a country. What if they joined together, to really lobby the government for massive change. Something that goes into law.
Like minimum wage increases, and the like.
The reality though is that any economic system is complex where pushing on one area creates an often unexpected result elsewhere.
You would also need heavier investment in government agencies that are meant to police the enforcement of such policies and to ensure that they are truly operating separately from the industries they are supposed to be policing. The opposite of that is what happened with the FAA and Boeing recently.