The game was ported to the Mac by a third party company, so the game is not exactly the same as the Windows version. While Feral Interactive does a good job at porting games...porting a game that way is not quite the same as designing the game for macOS.
Macs are not considered gaming computers like a traditional Windows PC. Plus you will want to ensure that your Mac meets or rather exceeds the Recommended System Requirements which can be very difficult to figure out.
My guess is you are using a Mac with an insufficient GPU (it definitely won't run with an Intel GPU), but it could be anything. You need to make sure to fully quit all other apps. Some apps may still run in the background, so they can cause performance issues.