Have you tried any of the possible solutions listed here?
https://melancholy-marionette.itch.io/bittersweetblythe/devlog/495925/opening-th...
It's a bit of a guide that I put together a while ago from various comments that Mac users made :3
Unfortunately, I don't own a Mac myself, or know anyone who does, so I can't test anything for Mac, and don't even really know how they work >.<
I don't know if it's still the case, but a while back, some Mac players told me that the easiest way to run indie games from here is to download the itch.io app, then download the stuff you want to play through that, and launch the games through the itch app.
They said it's an issue with Mac's security being too paranoid or something >.< haha. I didn't really understand everything they said, but it was something about Macs not liking 'unsigned' games, and most indie games are unsigned, so it causes issues launching them.
Thanks for checking out the project! And I hope one of the solutions folks came up with in the past works for you :3
(if not... I'm gonna need someone to chip in and help me figure out the best way to make stuff work on Mac, cos since I don't have one, I don't have a clue x3 I just have to trust that Unity's Mac export package works, and that Mac users can figure out workarounds for security issues and hopefully tell me so I can update the guide!)