I do post-it notes and a couple of master passwords for things I don't care about, so I don't disagree. I need to make 2 points though. 1, enough 'non-sensitive' data can eventually become sensitive when taken as a whole, and 2 post-it notes are less secure if they are at a place of employment, think teachers.
Maybe the best option is one of those physical access password managers like KeePass
KeePass on something normally-offline like a thumb drive is probably a decent compromise where needed, but I'd still encourage people to keep their most sensitive passwords either undocumented or partially/incorrectly documented.
Maybe the best option is one of those physical access password managers like KeePass