Many of those 'bugs' remain unfixed to maintain backwards compatibility, not because Apple doesn't want to fix them.
> the fact that it is officially deprecated sends a message to anyone wanting to do new development on MacOS “don't invest in OpenGL now as we could pull the rug under your feet” and it's done on purpose to push developers to Metal.
As it should be.
> So now they can only blame themselves if they're losing games because the developer doesn't want to invest in Metal either.
There's nothing to 'invest' in. Metal is by far the simplest low level graphics API out of all I've used and it would not be hard for valve to write a source 2 rendering backend for it (few days/weeks at most for an experienced dev). There's plenty of AAA games being properly ported to apple silicon now and in a year or two there will be many more. Valve intentionally withdrawing themselves from the ecosystem is purely out of spite.