As your model of Mac only has an Intel video system, that is probably the cause of your problem. This game now only uses Vulkan as a renderer, not openGL any longer. And Vulkan does not run well or in some cases at all on Intel video Macs. FYI this game has never been supported on that hardware platform since release, so really it's a matter of luck that it ever worked!
All you can do is revert to the previous game version in the Steam betas tab for the game. Or play on any other machine you have access to with supported hardware. OR if you have Apple Bootcamp installed, play in Windows there. Or, if you've just bought the game, seek a refund from that store.
Other options include ussing an eGPU, or a hosting service such as GeForce Now.
Sorry for the bad news!
