Here's some interesting reading material:
https://www.cloaked.com/post/the-top-3-worst-password-manager-breaches-and-security-issues-to-datePassword managers have been hacked in the past, and i'm pretty sure others will be hacked in the future.
Even if you use a local keypass, it can theoretically be bruteforced or you can fall victim to a keylogger.
The only safe setup i can imagine right now is a keypass database with a strong password on a removable encrypted medium (maybe a usb key with hardware encryption) that's stored in a secure location and that's only plugged in on offline machines, and it's probably a good idear to copy it on a second encrypted medium for safety.
Opsec-wise, i think that setup might even be safer than storing your seed on a piece of paper, as long as the offline machine you plug the thumbdrive into never ever goes online (maybe even has it's network unplugged and it's wifi physically disabled)It is true, however, that a lot of people store really important data in those password managers, there's no denying that... I'm 100% sure that a password manager is safer than re-using your password. Storing your seed completely offline also has it's attack vectors (like an evil maid, or burglars, or losing your seed), and it's correct that an extended seed with a strong custom password is a good idear.