Aren't Vulkan, Direct X 12 and Metal much closer than Direct X pre 12 and Open GL ever were? The three are derived (at least in philosophy) from AMD's Mantle, not like Direct X pre 12 and Open GL that are (or at least were) very different beast.
I only ever programmed with OpenGL 1.3 and 1.4, so my knowledge is not very up-to-date to say the least...