2D panels in VR are interesting for me, but not a killer feature. What would be a killer feature would be a VR designer for blender, unreal, unity etc.

Blender starts going there, but not yet for SVR: https://docs.blender.org/manual/en/2.83/getting_started/conf...

I think, this would be a way to really differentiate from closed platforms (which I also expect Apple RealityOS to become).

Unfortunately, the expectation that easy to use apps and tools for creating and consuming VR content will only be available only on closed platforms is quite reasonable.