]D3D9 is just an interface. If you change a remote control for your CRT TV it would not become LCD one showing FullHD quality programs.
The engine itself left unchanged, it's still 15-years old one. It knows nothing about how to use modern GFX cards or CPUs.
Ah ok, I see. It looks like there is still a lot of work to get the Ogre version to work well, and then to bring it up to a high standard.