Re: Sims 4 won't quit

You should be able to Force Quit the game either by clicking on the Apple logo in left hand corner of your screen or by using Option + Command + ESC. Granted this may not save your game, but you should be able to check your saved games by checking the time and date they were last saved. 

My advice would be once you force quit out of the game, to shut down and reboot your computer. You may also have to purge memory while playing to insure you have enough RAM to play the game.