I cancelled my subscription since I received a notification that my browser is not supported. Perhaps I should have mentioned my issues with DRM as well, but this may have gone too far. One message is clear, too many messages are noise.
Yes, disabling it doesn't remove it, but you can also remove it entirely if you want. Here are Mozilla's instructions (it's pretty easy). And here's Mozilla's post about implementing it, which also links to how to remove it. They supported completely opting out from day one, including opting out before Firefox has a chance to download the proprietary DRM code.