I partly agree. But your tone changed a lot from "highly insecure" to "less secure", which is a complete different statement. An application does not need to be in a sandbox to be secure, so I don't accept that as an argument against trusted applications. I only accept your arguments if we talk about random downloads from random places.

Also the argumentation that AppImages are usually run from random locations doesn't make them unsecure, it's a feature. BTW I have a dedicated folder where I put them, but that's my personal organization. Did you know that you can unpack an AppImage back to its original folder (like an archive)? You need appimagetool for that.

The only thing I fully agree with you and is a weak spot about the AppImage format is, that it can or will include outdated and not updated libraries (or executables). Which is the point of the format on the one hand, but a curse on the other hand. Normally it is recommended to build on the oldest supported LTS Ubuntu, because of older libc. libc is the root of many problems in Linux (for compatibility).