On top of that, OpenGL/Vulkan advocates tend to ignore that extension spaghetti makes them also completely unportable when extensions are only available for specific vendors, and if they are lucky with multiple vendors offering similar extensions, there is an exponential set of code paths only to deal with all of them.
Making them in the end hardly better than multiple backends, when doing serious stuff across multiple GPUs and OSes.
Making them in the end hardly better than multiple backends, when doing serious stuff across multiple GPUs and OSes.