Well that's disappointing to hear, I was hoping that with tessellation and the other upgrades Metal (and thus macOS) would (finally) be more or less on par feature wise with with at least OpenGL 4.4 and DirectX 11.
What's still missing?
This questions seems simple enough, but in fact, its very difficult to answer properly. The difficulty lies in understanding what exactly you mean with 'feature-wise'. First of all, I would like to make one point clear (subjective, of course, but anyway): Metal is a better and more convenient API than OpenGL, DX11 or OpenCL and writing high-performance, efficient and bug-free graphical and compute code with it is much either than with any of the direct competitors. Metal is a true next-gen API as it abstracts the hardware much better than OpenGL and DX11 and it has a lower overhead.
Now, if we are talking about 'features' as in 'things exposed by the API', I'd say that for all common cases Metal is feature-equivalent with GL 4.4 or maybe even parts of 4.5 and in fact, that it exposes hardware facts that no core OpenGL spec does. At the same time it is possible/likely that OpenGL does expose some features that Metal does not have. I am ashamed to admit that my knowledge of modern OpenGL is not as good as some years ago, so I will have difficulty pointing these out in detail. However, one can argue that many of these features are not necessary in Metal. Metal is a very compact, logical API that allows you to do many different things with very few means. Metal for OS X stick lacks synchronisation primitives (fences) — although they did introduce them for iOS 10 now - but they are less needed there as the command buffers can be queued/ordered explicitly. Metal does not have features like transform feedback or geometry shaders, but they can be implemented using compute and/or vertex shaders.
When I was talking about Metal lacking features for AAA games, I was thinking of comparisons to other next-gen APIs like Vulkan and DX12. Vulkan for example is very explicit in how you set up and treat hardware, which allows a competent dev to squeeze every ounce of performance out of the hardware — at the cost of complexity. Metal skips most of this explicitness, while still offering very competitive performance (in fact some of Vulkan features are borrowed from Metal, a fact that most people fail to acknowledge). The nice thing about Metal is that it is extremely easy to use and learn. This is by far the most straightforward graphical/compute API I have ever worked with and it is really a pleasure. The primary goal Apple had in mind (I believe) is offering an API that would allow an independent developer to build high-performance apps that utilise GPU across all Apple's platforms, and do it within reasonable time, with minimal effort. OpenGL has failed in that regard. Vulkan is barely unusable for a average dev (after looking at the specs, I am really afraid to even touch it). Metal hits the spot nicely. It does put more burden on developers when portion between platforms, but then again, it is straightforward to make a Vulkan implementation on top of Metal (AFAIK there is a company that is doing that at the moment).
