[MarkMc]

No. Here are two differences between a password manager and 2FA:

1. A password manager will prevent someone from hacking into a website you use, stealing your password, then logging into another website as you. 2FA won't prevent this because someone who hacks into to a website can get access to the unique random seed that is used to generate the 2FA sequence, and can then use brute-force to determine your password.

2. 2FA will prevent someone from infecting your computer with a virus, stealing your password as you type it in, then using that password to log in as you in future. A password manager wont prevent this because the virus will gain access to both your main password and the list of encrypted randomly-generated passwords.

[arnarbi]

Re 1: If a.com is hacked, only a.com's OTP seeds are compromised. b.com should (hopefully) use different seeds, so 2FA still prevents someone from logging in.

[MarkMc]

Yes you are right - I was thinking about the case where only a.com uses 2FA, not b.com