The community theatre down the street doesn't require every performer to be an cardholding AEA member, and it wouldn't make financial sense for anyone involved (management, workers, or audiences) for that to change. The mere existence of a union doesn't necessarily change anything unless workers want it to change.
For big game dev companies that have repeatedly shown that they don't believe in treating people fairly, this would bring professional representation to the workers' side. Even if the details are light at this point, I don't see how you can be against that in principle. The employer/employee relationship is inherently asymmetric, and this attempts to correct for that.
If I were a small non-union indie shop and I was lucky enough that some highly talented AAA developer wanted to work with me, I would be unable to hire him if he's union unless I converted my entire shop over to be union. If I didn't, he would be in direct violation of his union contract and could be fined or lose his membership.
I understand that not every union functions the same, but it is not hard to imagine that wherever there is a lot of money at stake the union will do everything in it's power, to well, seize power.
Considering the movie industry is dwarfed by the video game industry from a revenue point of view, I can very easily imagine this scenario repeating itself.
I've never heard of unions working like this, this may be a US-specific thing. Unions are just workers right groups, if the company is big, the group is inside the company, if it's too small, you just apply to the local union. They help to negotiate better laws and benefits for the whole industry & also directly at a company level in big companies.
I don't work in gaming though. I would love to, but the pay for business development is frankly better with a lot less stress. I wouldn't mind seeing a push legislating that any salaried worker in a week must be granted an extra paid day off at 45 hours and each 5 hours above in a single week. That would stop, or at least compensate, the abuse.
Addressing overwork at the legislative level would get my support if there were a way to trade pain now for benefit later (e.g. your extra time off suggestion).
Maybe unions can be useful after all!
The current unionization efforts provide almost no details on their goals beyond "everything will be better for everyone". On either end of the employee/employer relationship I have a hard time seeing how anyone can support such a generic effort.
A hard stance on working conditions and compensation is a starting point for a real conversation. The majority of employees would have no problem supporting this, and since I already value work/life balance and fair compensation, my motives and interests would align.