IE, DRM can't change peoples' motivations. It's useful for things like national security secrets and trade secrets, where the people who have access to the information have very clear motivations to protect that information, and very clear consequences for violating the rules that DRM is in place to protect.
In this case, the big question of if AI watermarking will work / fail has more to do with peoples' motivations: Will the general public accept AI watermarking because it fits our motivations and the consequences we set up for AI masquerading as a real person, or AI being used for misinformation? That's a big question that I can't answer.
If by "we" you mean anyone else than Google and the select few other LLM provider they choose to associate with, I'm afraid you're going to be disappointed.