Due a new issue with macOS Ventura, we've made some changes to Aseprite packages on Steam.
If you see the following popup when you try to run Aseprite on macOS, it's highly probably that you've updated your system to macOS 13.0 Ventura. Just press "Move to Trash" button:
Then re-start Steam, and press the Launch button on Aseprite, you might see an error like this:
But in a second try launching Aseprite, Steam will re-install Aseprite:
That should be enough.
In any case, if you have Aseprite installed and the problem still persists, you can right-click Aseprite and select Manage > Browse local files and delete the Aseprite folder:
Then re-start Steam, and re-install Aseprite. Restarting Steam is important because that leads to re-downloading some metadata about the new version that is available on Steam.
For more details: https://community.aseprite.org/t/aseprite-update-for-steam-on-macos-ventura/16229