I don't know if I think unions are a "problem".
I'd say that the problem is that the power that unions wield, doesn't really make sense as a whole.
For instance, when you work, your check is signed by the CEO of the company... Not the union in the place. People seem to forget that a lot.
I think Unions have done a lot of good, but I also think that the good that they do today is very diminished. Years ago, before the government was involved with standards of living and you needed to organize to get things done, I saw it.
I think organizing for safety and workplace environment is fine... Organized salary negotiations should not be a part of it.