Earlier quoted context omitted.
AppImage is not like the other two, it is fundamentally just a way to make a self-contained binary directory into a single runnable file - a way to avoid having to tell the user to extract a tarball and run a particular file inside. Convenience, nothing more. The other two define entire alternate runtimes.
No, an Appimage still ships a dynamically linked executable + lots of dynamically linked libraries, that only link against system libraries when strictly needed, e.g glibc and libGL. Those files are bundled in a squashfs and have a script setting a custom LD_LIBRARY_PATH to the squashfs content for the binary. Snap does use this technique, too, but does more, for worse. AppImages are not comparable with statically li…
Meanwhile, Snap and Flatpak are package managers - what's more, they're invasive heavyweights with permanent costs that are even worse than distro package managers. Snap permanently runs a daemon, and Flatpak requires you to run programs with "flatpak run" - yuck! They are both trying to impose some dubious vision of sandboxed apps that require bureaucracy to communicate with each other, instead of just tackling the core issue of software distribution. Maybe you even like sandboxing! But I've seen no justification why that should be co-mingled with package management.