Most Mac computers come with really crappy Intel GPUs lime the HD 4000, which are terrible for gaming and in this case, if you have them (and you probably do), then they are the source of your problem.
If it's a desktop you might be able to switch out the GPU for a card that can run shaders, like something decent from NVIDIA, but im not sure if even Mac desktops work well for that sort of thing.
If you have a Mac laptop you're pretty much screwed lol
Live and learn. Get a Windows computer next time if you can.