Researchers found that almost every victim was a LastPass user.
More than $35 million has been stolen from over 150 victims since December — ‘nearly every victim’ was a LastPass user::Security experts believe some of the LastPass password vaults stolen during a security breach last year have now been cracked open following a string of cryptocurrency heists
The idea is fine. Still trusting lastpass was the bad idea. Others have much better implementations to protector your vault and don’t drop the ball on security time after time.
Personally I don't like to rely on anyone's cloud services for mission critical applications like password storage, since they have a history of being discontinued without notice.
I do trust Mozilla a lot more than Google, though.
With Syncthing at least if the discovery servers go down you still have a local copy as well as off-site backups, and can easily migrate to some other sync solution as your password manager is not tied to your browser.
I would argue that email is similarly as critical, yet Selfhosting email is a bad idea practically and from a security standpoint. Your argument does not apply in general.