Ultimately, the new APIs are designed to cure all four of these problems.
* Why are games broken? Because the APIs are complex, and validation varies from decent (D3D 11) to poor (D3D 9) to catastrophic (OpenGL). There are lots of ways to hit slow paths without knowing anything has gone awry, and often the driver writers already know what mistakes you're going to make and are dynamically patching in workarounds for the common cases.
* Maintaining the drivers with the current wide surface area is tricky. Although AMD and NV have the resources to do it, the smaller IHVs (Intel, PowerVR, Qualcomm, etc) simply cannot keep up with the necessary investment. More importantly, explaining to devs the correct way to write their render pipelines has become borderline impossible. There's too many failure cases. it's been understood for quite a few years now that you cannot max out the performance of any given GPU without having someone from NVIDIA or AMD physically grab your game source code, load it on a dev driver, and do a hands-on analysis. These are the vanishingly few people who have actually seen the source to a game, the driver it's running on, and the Windows kernel it's running on, and the full specs for the hardware. Nobody else has that kind of access or engineering ability.
* Threading is just a catastrophe and is being rethought from the ground up. This requires a lot of the abstractions to be stripped away or retooled, because the old ones required too much driver intervention to be properly threadable in the first place.
* Multi-GPU is becoming explicit. For the last ten years, it has been AMD and NV's goal to make multi-GPU setups completely transparent to everybody, and it's become clear that for some subset of developers, this is just making our jobs harder. The driver has to apply imperfect heuristics to guess what the game is doing, and the game in turn has to do peculiar things in order to trigger the right heuristics. Again, for the big games somebody sits down and matches the two manually.
Insight into graphics API development: Mantle, Vulkan, and DX12
