Unions protect labor from the forces of capital who take advantage of them. See: the recent WGA strikes and the protections from AI work that they now work under.
I think the point is it becomes irrelevant how good of a contract hollywood actors get if hollywood is cut out of the picture entirely by smaller independents using AI.
How does a union contract stop me from making something at my kitchen table?
The union contract is between some Corp and their employees
The Hollywood strikes seem rooted in 1985...no one needs Hollywood to make or consume content anymore