Apple Passes are a feature built into Apple Wallet, which is iOS/watchOS/Safari-only. Google has their own version in Google Wallet that runs on Android (and only Android with Google Play Services if I recall correctly). Samsung has a version too and there are many others. I believe they all operate off .pkpass files.

Apple Pass Designer is just a tool for customizing what the passes a business is giving to its iOS customers looks like. It's macOS-only (Apple barely supports anything not-Apple). I assume the customizations won't translate to other apps unless those apps add support, but the passes should still work.

It’s made clear that this is specifically for Apple Wallet, not some sort of general solution.