Your parents are more likely to be a victim of a phone call scam than malware, even on PC. There is also no guarantee that malware will not slip through cracks of official stores or signatures.
You can also choose to do your banking at the physical branch.
We already had "best of both worlds", especially on mobile OSes - granular permissions per-app were quite good, and on Android until few years ago root was widely available if you needed it as well; these permissions could be locked or frozen if there is concern about users, just like work devices are provisioned with limitations. It all depends on your threat model.
You can also choose to do your banking at the physical branch.
We already had "best of both worlds", especially on mobile OSes - granular permissions per-app were quite good, and on Android until few years ago root was widely available if you needed it as well; these permissions could be locked or frozen if there is concern about users, just like work devices are provisioned with limitations. It all depends on your threat model.