"Content is king!" Have you never heard that before?
You say Mozilla should figure out what will draw users from other browsers, but you've outlined what will draw users from Mozilla to other browsers. In the end, people want content. The content providers have more control. If 70-80% of the browsers already support the DRM they want to use, the other 20-30% will follow or be left out. Which is exactly what happened here.
There is tons of content on the web that has nothing to do with video. There is tons of video on the web that has nothing to do with DRM. If there is 20% of web surfers excluded by Netflix and Youtube, and DRM in fact doesn't matter for securing sales, then that's a huge edge for any new content provider that wants to compete with the incumbents.
All of that said, yes, of course this is something that will serve as a draw for users away from Mozilla. And yes, of course Mozilla might not be able to find something else that can serve as a better (or even comparable) draw that will not compromise their principles at least as much. I'm not casting aspersions at Mozilla and saying "Gee, they're dumb, why don't they just...". I'm saying "It would be better if they had found X" where I'm not at all sure such an X exists.
You say Mozilla should figure out what will draw users from other browsers, but you've outlined what will draw users from Mozilla to other browsers. In the end, people want content. The content providers have more control. If 70-80% of the browsers already support the DRM they want to use, the other 20-30% will follow or be left out. Which is exactly what happened here.