Why do you believe the copyright holders (or the browser makers) are the ones who potentially hold absolute power in this scenario, rather than the users? Any DRM is an unsustainable system, EME is not going to change this. I also have strong doubts that EME will do anything to push the so-called "content industry" towards better sustainability as you suggest it will. There is still zero incentive for any knowledgeable user to buy into it. If anything it will just make the system more complicated because of the proliferation of even more competing, incompatible DRM systems that only work on certain devices with very specific configuration requirements.
I agree that some of the ridiculousness in the DMCA is part of the problem, but this isn't going to be solved by building more walled gardens, it's going to be solved by thinking about how it can actually benefit the user in the long run.