I worked for Microprose in the 90's. Back then we had direct access to hardware, but the technology was limited. GFX power increased and new tricks came. Now a days it wouldn't be possible to do all that.
DirectX is the sole reason we have good games and graphics on PC. No one wants to reinvent the whole wheel and Microsoft works a lot with GPU manufacturers to come out with new technology.
DirectX is not the reason, it's the lazy developers who just port the game from consoles to PC. They don't spend the time to make a PC version that uses DirectX and newest graphics cards to their fullest capability, so why on earth they would do that if you remove DirectX.
There is no DirectX on Linux and just look at how laughtable the situation is. Yeah theres nethack and some clone of Civilization 2 with worse graphics, but it's far from both console games and PC games that gamers play. It's a joke.
Microsoft has supported PC gaming to great lengths. We all should thank Microsoft that the situation is even so good. Who we should bitch at are the lazy developers and AMD, who also has been lagging behind. NVIDIA and Microsoft is basically doing all the innovation, and their hardware is miles ahead of AMD's. Microsoft, Intel and NVIDIA. All great companies with great products that are truly working for PC games.