It's a bummer that developers don't update this game to support newer MacOS but gamers managed to figure it out.

I'm not the author, I just found this guide on the Internet, thought it might be helpful to put it here.

How to port Windows, Linux and 32-bits macOS Unity games to run on 64-bits macOS [github.com]

Follow the guide, you should have no problem running this game on the latest MacOS (I've tested it on M2 Macbook with MacOS Sequoia).

ATTENTION:
* You can find the Unity Engine version to download here [github.com]
** The only catch is you should specify the launch options in steam property page as -force-glcore for better performance.