Joy2Key is not available for Mac but there are some alternatives that runs on macOS with similar functionality. The best Mac alternative is SDL2 Gamepad Tool, which is free. If that doesn't suit you, our users have ranked more than 10 alternatives to Joy2Key and five of them are available for Mac so hopefully you can find a suitable replacement. Other interesting Mac alternatives to Joy2Key are Joystick Mapper (Paid), GamePad Companion (Paid), Controllers (Paid) and ShockEmu (gamepad fork) (Free, Open Source).
Joystick Mapper is an application that allows you to configure your joysticks or gamepads to simulate keyboard keys/mouse movement/mouse click/mouse scroll, so you can control any app or game using them, even the ones without built-in support.