I believe (hope) that OpenGL continues to be that developer-friendly API. Building OpenGL on top of Vulkan shouldn't be too hard, and it means we don't have to pointlessly deprecate and recreate the huge number of OpenGL resources out there.

OpenGL isn't friendly to developers on either side. Tutorials are generally not trustworthy, there's no cross platform debugging tools, and errors just get you a "something happened vOv" code.

If you care about performance it will just do something slow at uncontrollable points in the background, like copy CPU-GPU-CPU memory, synchronize against the GPU, do format conversions, etc.

If you're the one implementing GL, it's gotten gigantic again since they simplified it. GL 4.3/4.6 core has compute shaders, which means you have to implement OpenCL twice but different this time.

There is already OpenGL-on-Metal and OpenGL-on-DirectX middleware, so this may not actually be an issue.

Then you could just use one of the existing engines like Unity.

Pretty sure Unity is more heavyweight than a few hundred kilobytes of a library.

It also doesn't come installed on my machine.

Depending on the project type, the final release package can be just a few hundred KB, like they do when targeting WebAssembly.

OpenGL also does not come installed on my machine.

Right, but it still involves several gigabytes of largely unused functionality to get a “hello world” and it pigeonholes you into a specific ecosystem. Unity is an entirely different offering from a graphics api.