It is hard to make super-simple software that also caters to every use case. We try to make it as simple as possible for as many use-cases as possible. We do maintain that the key sharing functionality is so much better than the shared passwords used with AxCrypt 1.
You can always turn of the “auto-upgrade” of old files, so you can maintain them unchanged in AxCrypt 1 format and with the old passwords.
Nobody with access to your computer can read any encrypted files as such, however, anyone with access to your computer with your user rights and permissions can install any software on it so if you allow that you are insecure by default, regardless of AxCrypt-version or other software used.