My 2FA OTPs are synced by 1Password which I can access from any of my devices; you can set up something similar with FOSS if you want full control. Authenticating to 1Password requires both a master password and a secret key; they have a feature called "Emergency Kit" for creating offline backups of the key (https://support.1password.com/emergency-kit/)
Using a password manager introduces a single point of failure. My biometrics are leaked every time I post a selfie or a picture of myself holding something. The idea of something like an "emergency kit" being extant for something I care about makes my skin crawl. They say you should put it in you cloud storage!!! What the actual fuck. The only points of vulnerability in the chain for the things I have passwords on is keylogging or a system breach on the provider side. I can rest easy that until I have my brain chip I'll lose at most one thing at a time. There is zero chance of a massive failure, and there's a very low chance that I'll lose access because some part of the chain is missing, and my vulnerability surface is much lower than if my passwords existed anywhere outside my brain.
In any case, I'm far far more worried about not being able to log into something because there's too much security than I am worried about someone accessing my things when they shouldn't. The former has cost me many more productive minutes than the latter.
I have about 300 logins and my memory ain't so good after too many hits to the ol' noodle. You don't expect me to remember all of those without a password manager? I'm much more worried about the SPOF inside my skull.
Oh, yeah well that makes sense. I only have to remember something like 20. SaaS is bad and you shouldn't use it but I guess if you have to then them's the brakes kid.
Your password can still be a secret unbound from any physical object. This is just a second layer, so I don't really see the downside
EDIT: I guess you're right in that the parent was suggesting NOT typing passwords and sort of equating that to 2FA. so yeah, I like to keep one password in my head only (for sensitive stuff) and use a second factor if possible
The second layer is the downside, it makes it annoying to log into stuff. Even using SSH keys is awful. The UX of being able to log into things from wherever on whatever device because you remember your password is unparalleled. Yeah you have to worry about being keylogged which like, sure, it's a worry, but I've spent a lot more of my life being annoyed that I couldn't log into something because I didn't have the SSH key on that machine or trying to find my stupid yubikey etc than I have dealing with the afermath of having something hacked.
(which to my knowledge only happened once when I set the root password on my VPS to 'toor' before i knew about internet background hacking radiation, and sure maybe i'm compromised right now, but it's absolutely not affecting my day to day life so i'm not gonna worry about it)
Certain crucial passwords can be kept in the memory. There are thousands of menial logins though and a password manager might be more reliable than the memory