Are you shutting down all non-essential programs before starting the game, especially anti-virus and any backup programs that may be monitoring the Documents folder?
At least in Windows, several anti-virus and security programs have blocked the game from being able to create folders.

Try doing a clean boot and then test the game. Start/restart your Mac and hold the Shift key down as soon as the progress bar comes up in the startup window, releasing it after the desktop appears. Alternately, from the login window, hold the Shift key when you click the Log In button, and release it when you see the Dock.

Try creating a new OSX administrator user account (either with the Documents folder in the default location, or on a different drive, if available), switch to that account and try starting the game from there.


Try browsing to the '~/Documents/Larian Studios' folder and delete the 'Divinity Original Sin Enhanced Edition' subfolder.
This folder contains the saved games, configuration files and a level cache folder. Normally I would suggest renaming the folder for troubleshooting purposes, but if you don't have any saved games that isn't an issue.
Next, extract the replacement folder from this download into your '~/Documents/Larian Studios' folder, and see if that will let you start the game, create a new profile and/or start a new playthrough, get into the game and save.

The graphicSettings.lsx file is set to 1280x720 Windowed mode, Very Low quality preset, which you can change in the options (manually, or hit autodetect) if this helps.