It's also somewhat good for the web since both of those platforms are competitors and companies often reuse things they've already invested in.
It is unequivocally bad that it poses a risk to Mozilla but the real problem isn't EME but rather the fact that all of the DRM opposition since the 90s has failed to move public opinion much. As long as customers happily pay for DRMed content and three of the major browsers are made by DRM vendors, the most likely alternative to Flash is a proprietary interface. The fact that EME is standardized at least gives the EFF better grounds for demanding consistent treatment.