I do not see any difference between writing passwords in a piece of paper vs saving passwords in the browser in its default unencrypted form without master password. In fact I would say writing password in a piece of paper becomes a bit more secure compared to saving passwords in the browser because you can at least be responsible enough to hide that piece of paper in a safe compared to passwords saved in your browser which is always two clicks away.
Someone with two cents of security needs can use master password to encrypt the password but it is not what majority do. For majority of people, their passwords is just in the Passwords option in the hamburger menu. This can definitely be improved.
There are two easy ways to set it up I see,
1: Make master password mandatory and warn the user they cannot forget it. If they do not provide master password, they cannot save passwords in the browser, as easy as that.
2: Disable the option to view passwords if done in an insecure way, meaning if there is no master password present. This is not full fledged solution but will help against most normal computer users. Surely a 'hacker' can find the passwords file somewhere in the computer and open it up with notepad but that is statistically not most people