Even if you had access to DX9 APIs, what are you going to do with them that you can't do in DX7? Once you can answer that question, THEN you're in a position to start complaining Blitz3D isn't enough.
Point sprites for speedy particle systems, vertex shaders for skeletal animation that isn't dog slow, pixel shaders for bloom and all those lovely post processing effects that are horrendously slow when you have to fake them. Can I complain yet? :)