As I haven’t seen other websites than such movie streaming sites using DRM, I don’t think it’s another mail in the coffin. It doesn’t actively hurt anyone, and it does not stop shows to be ripped and released on tpb. It’s just an alibi for movie makers.
So, what’s the fuss about it?
As you pointed out, content will still be ripped so, once again, this only serves to inconvenience the users. But browsers won't force you to use netflix & al. so it's up to the user to not use those sites.
If I'm gonna shout at firefox, the fact that they aren't first implementing CSS features that the internet has been waiting for forever is probably a better reason.
It's really simple: You either use sites with DRM and thereby accept it, or you don't. There's no point in crying about how browsers shouldn't even give you the choice.
If anyone applies DRM on html, you can't even use ad blockers anymore.