I say the problem lies in with the unions that represent them. Much like many unions in the private sector, they are working with an outdated business model. They act like it is still the 50s and 60s. What worked then doesn't work now. You are working with a world business model, not a country business model. It is a global economy after all.
Even today, they rather fight a company that work with them. That is something that makes absolutely no sense. They prefer confrontation instead of collaboration. The union mentality is still to whine, fuss, cry, and stomp about. Do not give an inch. If the money isn't there, stay firm and make the company give in. If they threaten to move jobs to another state or country, call their bluff. Then go on strike!
Thing is, that doesn't work. Companies will move the jobs to a friendlier climate. Why was Mercury Marine willing to shift production to Oklahoma from Wisconsin? The workforce was going to give them the flexibility the modern factory needs. Same with Harley Davidson. They could move production to Pennsylvania and Kansas City where they could save money. In both cases, the unions were against the deal that the company offered. Thankfully, union members were smart enough to take the deal against the advice of union leadership.
The answer for this is quite simple. Unions need to work on quality, not quantity of its members. Companies will pay good employees an above average wage. Many people will scoff at that suggestion but is is true. Culvers is a good example. They have always paid above the minimum wage because they want to attract a workforce they know will work hard and that they can reward.
If a company wants to skimp on pay, they will find themselves with the worst workers. Good employees will move to jobs that pay better and offer a better work environment. That is how the job market works.
Of course the unions could take it one step further and push for profit sharing but if that happened, then the union really wouldn't be necessary. Much the reason for fighting management instead of working with them. They rather use the outdated model of fighting instead of proving that their workforce is the most valuable asset the company has.