Linux is not ready for gaming, Valve is making a huge mistake. Developers will try and encounter tons of problems like that and most will abandon the port project. Just going from DirectX to OpenGL is a lot of hard work for nothing from a graphic programmer stand point.
No, the purpose of DirectX is to make the best graphics API available so that developers use it, and it's doing an awesome job at it. The fact that is not cross-platform is only because Microsoft don't see any advantages at working for free and doing it, why would they?
Your post prove that you got out of computer graphics long ago, because it's quite ignorant. The game changed a lot since you checked it, and no, it's not just polygons and shading anymore, or else games would look like total shit like that 2000's era.