I encountered this issue as well. The way I fixed it was by ctrl-clicking, selecting "Open with" and then unzipping the file with The Unarchiver instead of Mac's default Archive Utility. The latter breaks a lot of indie Mac games. If you don't have The Unarchiver downloaded, you can get it on the Mac app store here: https://apps.apple.com/us/app/the-unarchiver/id425424353?mt=12
Sometimes you'll encounter a different error saying "App is damaged and can't be opened." In that case, go into Terminal and type "xattr -cr /Applications/Default.app" (minus the quotation marks, and replace "Default" with the name of the application. Also, before you do this make sure you have the game in your Applications folder obviously) Here's more info: https://osxdaily.com/2019/02/13/fix-app-damaged-cant-be-opened-trash-error-mac/
Edit: if you do both of these things and you're still encountering an error, follow the instructions for using the chmod +x command posted further down by user maxybaer123 (the person I'm replying to)