Thanks for explaining this! Unfortunately, Apple has made it difficult to distribute apps outside of their ecosystem lately.
Another thing that may be relevant. A user in another thread mentioned this to me:
"i just extracted the zip using the unarchiver app instead of the default app and it worked just fine. even with the new catalina update"
Perhaps the default unzipper strips the +x flag? It might be easier for some users to use a different unarchiver app to workaround this issue.
I can second this claim! I don't really know how it works, but using Unarchiver to extract the zip file seems to be a more easier solution to the problem than the one with the Terminal. This also worked with one other game that initially wouldn't open on Mac Catalina for me. Also, if anyone needs more help or steps with this method, I can make a new comment explaining the whole process over.
Ah, here's the new comment explaining the whole process in case you didn't see it yet!