As bitmover said, it isn't at all practical to store passwords on paper. In addition to having to leaf through them looking for the credentials, it is insecure by definition, because if someone finds your notebook, if it is a malicious person, your passwords have been compromised.
I get your point. Although some notebook comes with bookmark, where you can use it to split it either by alphabet or category (e.g. social media, exchange).
How do you generate these passwords? Are they being generated randomly? Password managers solve this problem.
FWIW, you could use password manager only to generate the password and write-down it on paper.
I Think the point is that we generate new passwords nearly every week.
Will you carry that piece of paper with you all the times? Yesterday I had to create a new account in a website to buy some suplements.
Then, a few days ago, I had to create an account in a new airlines company which I never used to travel to a place I have never been.
I used a password manager which syncs with my phone, so I don't need to care about noting those passwords down in a paper if I am not home when I create those accounts, for example.
It is very convenient and protonpass is safe. As I said, I see no problem if someone is able to login into this airline company with my email,. He cant buy anything, just see my past trips.