It can be. Single master password, if leaked or otherwise getting into the wrong hands, gives access to all your auth details. This is part of why I keep to a d

It can be. Single master password, if leaked or otherwise getting into the wrong hands, gives access to all your auth details. This is part of why I keep to a desktop based password manager rather than an online one. But it depends on your threat model and attack surface area/shape. A strong password on a post-it on your monitor is stupidly insecure locally, but far more than just having a weak password if you consider only non-local (to the user) attacks (neither that site hacker in far-off Hackyoustan nor his pet bots can see the post-it, but could try brute force a short easy to remember password).