So basically Linux OS & Company (All other Linux OSs) is a Giant Sandbox Application OS where apps/snaps can run w/ limited or restricted access to main resources?
Most Linux distros are built to be well integrated and to work by using a somewhat custom kernel tree. All applications require certain drivers, modules, and the kernel itself. Some applications run in privileged user space (root), some applications run in non-privileged user space (you). I would not characterize the kernel as a sandbox, and I would not characterize apps as independent of what the kernel provides.