Password managers are already pretty easy to use from a nana's perspective. The main problem is that nana does not know that password managers exit itself. Most of them just input password as 'nana1234' and store it in their browser password manager (usually chrome password manager) and use chrome's autofill.

Eg., I was telling a middle aged person (50 years) about password managers and were unable to grasp the idea of it. 'Why would you store passwords in cloud based password manager from a company I have never heard of, just type a password and write it down on your diary (OS notes app) or just store it in chrome. I trust google (chrome) to keep my passwords safe rather than with some sketchy company I have never heard of (the sketchy company if one of the most reputable cloud based password management company).