Use a password manager. Let it generate and remember passwords. Built-in to MacOS/iOS/iPadOS, including MFA. I switched my parents to iPads a few years ago, terminating my frustrating pro bono IT support contract with them.
I had a similar issue with my parents.
The most common problem is signing up for new services on their phone. On their Windows computer, in a web browser, their password manager's browser extension is great at suggesting generated passwords and saving new accounts. But on mobile it takes a few steps and app switches, which they don't love (and one parent forgets and often has to go to the other for help).
Logins are usually well integrated (my family uses iOS, and Dashlane; I assume 1password works just as well)