That's what can be achieved by encapsulation/containerization of apps: a la flatpak, snaps, docker or VMs... I found my parents to install random crappy adware

That's what can be achieved by encapsulation/containerization of apps: a la flatpak, snaps, docker or VMs... I found my parents to install random crappy adware apps from official stores too. What protects their banking application is granular permissions, not root access.