Yes, I use a password manager too, but an ancient one that has no Internet connection, no syncing, and no cloud storage.
The only "modern" password manager I've been able to find that works completely offline and is open source is KeePass -- so long as you don't install any of its plugins that open it up to Internet access.
Kind of a secondary master password that's not stored anywhere except my memory and my safe.
Best of both worlds in my opinion.
A great thing about password managers is that you can change your passwords more often since you don't have to bother coming up with and remembering new passwords. It can even be somewhat automated with pass-rotate: https://github.com/ddevault/pass-rotate
While I agree that this would be a security disaster, its not a whole lot different then someone using the same credentials for all their accounts. Also, one of the great benefits of a password manager is that they remove a very high mental cost of passwords. Before I used a password manager, although I knew it was good practice to change passwords, I wasn't willing to invest that effort into it. The cost of good random passwords was too high. Today, if my password manager was hacked, it would suck going through all my accounts and changing all the passwords - it would take a lot of physical time, but there would be no long-term fallout and mental effort involved for me. I'm not attached to those passwords - I don't even know them.
Personally most non-trivial passwords of mine were generated by 'pass'.