Yes, OpenGL on macOS is now implemented over Metal, but unfortunately a side effect of this is that implementation-level details that were critical to debugging and profiling OpenGL just no longer exist for tools to work with. Anything is possible? Maybe? I'm sure Apple Graphics engineers could make old tooling work with the new abstraction layer, but it's not happening.
Tooling investment is all on Metal now. But so much existing NON-LEGACY software relied on OpenGL.
So what do you do? You debug and perf test on Windows and Linux and hope that fixing issues there addresses concerns on macOS, and hopefully your problems aren't platform-specific.
This is how some graphics engineers, including myself, continue to ship for macOS while never touching it.
Edit: Also, Vulkan is a waste of time for anyone who isn't a large studio. No one wants to write this stuff. The most common argument is "You only write it once." No, you don't.
You have to support this stuff. If it were that easy, bgfx would have been written in a month and it would have been considered "done" afterwards.