[azakai]

It's more like standardizing a road that only Google, Microsoft and Apple and their partners can drive on.

An open standard is one that anyone can implement. EME is not open in that way - it just standardizes a small part, the interface. The DRM itself remains completely nonstandard, and Google, Microsoft, Adobe etc. all have their own proprietary DRM products. So a browser that actually wants to show EME content must partner with them. That's the opposite of an open standard.