Of course, HTML5 video is supposed to make video on the web more standard and easily available, but DRM means you need every CDM to support both your browser and OS...
The whole point of CDMs is to prevent users from doing things (e.g. taking screenshots or clips of videos for fair use, or backing them up, or pirating wholesale). You can't claim that this is empowering users.
Any effective CDM implementation requires a media company having final control over the user's computer (or a nested computer as provided by TrustZone or SGX). This is not compatible with user freedom or security.
This seems like the opposite of what Mozilla is supposed to be working for. If Mozilla can't exist without market share, and they can only have market share by giving up on user freedom, then simple modus ponens tells us that Mozilla can't exist. If this is the case, those interested in continuing to pursue the goals of empowering typical computer users should look into some form of praxis more effective than developing a Web browser.