Hello, maybe your folder isn't called 'Downloads' but is translated into a language other than English? As for me, I installed the itch.io application on my Mac, then installed the game through the application. I didn't follow the instructions as recommended. I click on 'Launch,' the game crashes, and a Mac OS message asks me if I want to relaunch. I click on 'Relaunch,' and the game starts!
Unfortunately Apple has made it very difficult to release third-party programs on their platforms; I'm not sure what the exact issue is with your initial report (haven't received such a report before), but my hunch is that it's related to the "this program is from a third party and thus can't be trusted" set of hoops Apple requires developers to jump through. If you're still interested in giving it a go, when you try to open the game and whatever error appears, go to your computer settings, then to the security tab, and scroll all the way down; it might be that the program is listed there as having been blocked by Gatekeeper, and you should be able to say "Run Anyway" to permit the game to be run.
