I think you seem to not realize how much time it would take to do what you suggest. Ultimaker has grown quite a lot the past few years, but there is a limit to the amount of testing we can do. So that means we have to make choices. Which also means that we don't test on every single setup that we theoretically support (or even close to that).
That being said, there have been multiple issues with OSX in the past with speed. Some of them are actually completely out of our control as they were caused by the framework we used (and the smouldering hatred apple seems to have for developers). This in turn leads to us not even being able to support older OSX versions because we can't build for them (or if we did, we'd have to spend so much time and money on it that it would cost far to much).
So yeah, I get the frustration. I really do. But calling people out when we are trying to resolve your issue isn't helping (and especially not if they, unlike me, aren't even paid to do so ;))