There is no simple answer. Its is almost entirely dependent on implementation. All systems are vulnerable to things like supply chain attacks. We put a lot of trust in phone vendors, telcos and Google.
If you are going to compare to something like termux you need to compare with an equivalent sandboxed environment on regular linux, like a docker/podman container with appropriate permissions. As far as I know they use the same linux kernel features like cgroups and namespaces under the hood.
Traditionally Linux desktop apps run with the full permissions of the user and the X window system lets apps spy on each other which is less secure than Android sandboxing by design. There have been attempts to do better (eg flatpak/flatseal, wayland) but they are optional.
We keep it out of habit and because the Government bribes us.
Some people probably get good value out of it but not us. There is a lot of faith healing stuff on their policies and those practitioners rely a lot on over-servicing for their income so the people into that shit likely make claims. Partner went into hospital once and I said why didn't you use the card to get a room upgrade with nicer wallpaper and its basically not worth the effort. I'm not complaining because if they were offering value it would be at the expense of the public system and peoples health. They overcharge for policies that are basically useless and never get claims but as long as they can lobby politicians it keeps them in business anyway. They should let people add their pets to the family policy, then we might find some use for it.