> What's confusing is having a zillion usernames and passwords for every site on the internet, and "doing it right" (which only a tiny percentage do) requires installing password manager extensions in your browser. In practice billions of users use the same insecure password everywhere including their banks.

That should be OS level. The fact that the OS does not provide good, lightweight ways for mortal users to whip up additional user-accounts for guests and family-members without breaking a lot of things should not mean that Google makes their own into the browser and adds yet-another-layer-of-login.