Two factor authentication is nothing more than a massive vulnerability. We've seen people somehow change our listed contact numbers through unknown exploits, then hijack ownership of properties using the new number to prove they are us. This wouldn't be possible if not for 2nd factor authorization schemes.
And, as others have mentioned, it increases the likelihood of getting locked out of your accounts (if you don't have your phone with you or the battery died or whatever). Which encourages service providers to make account recovery easier (it needs to be easier if people are more likely to get locked out.) And making account recovery easier makes it easier for other people to 'recover' your account.
3rd-party authentication (other people vouching that you are who you say you are) might be better, but would have its own problems.
In the end, the real solution to the problem of 'what if your password manager gets compromised?' is to minimize that possibility by _not_ having it online, having really strong master password and/or keys, and avoiding malware. 2FA doesn't help with that at all. It just adds its own problems.