> If I'm using the App Store stuff, then my text editor can't edit all my files, my video player can't open videos when I double-click them, my Evernote can't print to PDF, my disk usage analyzer can't analyze my disk because it can't ask me for authorization to do so, and so on.
I fail to see how the macOS sandbox prevents this. Disk usage analyser can ask you for disk access, sandboxed video players can surely open files double clicked in Finder, sandboxed apps can print to PDF.
A few example: QuickTime Player is sandboxed, Pages is sandboxed.