Mojave will not install if you have a non-metal supported GPU. Despite the annoyingness of having to meet the requirements, it was a necessary evil. Vulkan, the OpenGL successor, wasn't quite ready for primetime when Apple originally created Metal for iOS and thus decided to port it macOS. OpenGL has been a thorn in Apple's side for quite some time, as it's been nearly dead for years. The biggest change for macOS Mojave is the deprecation of OpenGL and OpenCL.
